MCP401x/2x - Electronic component Microchip - Free user manual and instructions

USER MANUAL MCP401x/2x Microchip

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Table of Contents

Preface ....1

Chapter 1. Product Overview

1.1 Introduction ...... 5
1.2 What is the MCP402X Digital Potentiometer Evaluation Board? 5
1.3 What the MCP402X Digital Potentiometer Evaluation Board Kit Includes ..... 6

Chapter 2. Installation and Operation

2.1 Introduction ...... 7
2.2 PCB Description 7
2.3 Test and Operating Instructions 10
2.4 Firmware Description ...... 17

Appendix A. Schematic and Layouts

A.1 Introduction 19
A.2 Schematic 20
A.3 MCP402X Board Layout – Top Layer + Silk-screen 21
A.4 MCP402X Board Layout – Bottom Layer 21
A.5 MCP402X Board Layout – Top Silkscreen 22
A.6 MCP402X Board Layout – Bottom Layer + Silk-screen 22

Appendix B. Bill Of Materials (BOM)

Appendix C. Using the BFMP Programmer to Power the Board

C.1 Powering the Board Using the BFMP Programmer 25

Appendix D. Potential Programming Issue of the MCP402XEV

D.1 Introduction 27

Appendix E. 00066\_MCP402XEV.ASM Source Code

E.1 Introduction 29

Worldwide Sales and Service 42

NOTES:

Preface

NOTICE TO CUSTOMERS

All documentation becomes dated, and this manual is no exception. Microchip tools and documentation are constantly evolving to meet customer needs, so some actual dialogs and/or tool descriptions may differ from those in this document. Please refer to our web site (www.microchip.com) to obtain the latest documentation available.

Documents are identified with a "DS" number. This number is located on the bottom of each page, in front of the page number. The numbering convention for the DS number is "DSXXXXXA", where "XXXXX" is the document number and "A" is the revision level of the document.

INTRODUCTION

This chapter contains general information that will be useful to know before using the MCP402X Digital Potentiometer Evaluation Board. Items discussed in this chapter include:

• Document Layout
• Conventions Used in this Guide
• Recommended Reading
  • The Microchip Web Site
• Customer Support
  • Document Revision History

DOCUMENT LAYOUT

This document describes how to use the MCP402X Digital Potentiometer Evaluation Board. The manual layout is as follows:

- Chapter 1. “Product Overview” – Important information about the MCP402X Digital Potentiometer Evaluation Board.

- Chapter 2. “Installation and Operation” – Includes instructions on how to get started with this evaluation board.

- Appendix A. “Schematic and Layouts” – Shows the schematic and layout diagrams for the MCP402X Digital Potentiometer Evaluation Board.

- Appendix B. "Bill Of Materials (BOM)" – Lists the parts used to build the MCP402X Digital Potentiometer Evaluation Board.

- Appendix C. "Using the BFMP Programmer to Power the Board" – Shows how to interface the BFMP board with the MCP402X Digital Potentiometer Evaluation Board.

- Appendix D. “Potential Programming Issue of the MCP402XEV” – Discusses possible programming issues with Rev 1 and Rev 2 of the MCP402X Digital Potentiometer Evaluation Board.

- Appendix E. "00066_MCP402XEV.ASM Source Code" – Provides information about the application firmware, as well as the location of the source code.

CONVENTIONS USED IN THIS GUIDE

This manual uses the following documentation conventions:

DOCUMENTATION CONVENTIONS

Description Represents Examples
Arial font:
Italic characters Referenced books	oks	MPLAB ^ IDE User's Guide
	Emphasized text ...is the	only compiler...
Initial caps A window the Output	ut window
	A dialog the Settings dialog
	A menu selection select Enable	Programmer
Quotes A field name in a window or dialog		"Save project before build"
Underlined, italic text with right angle bracket	A menu path	File>Save
Bold characters A dialog button	Click OK
	A tab Click the Power tab
'bnnnn	A binary number where n is a digit	'b00100, 'b10
Text in angle brackets < >	A key on the keyboard	Press,,
Courier New font:
Plain Courier New	Sample source code	#define START
	Filenames	autoexec.bat
	File paths c:\mcc18\h
	Keywords	_asm, _endasm, static
	Command-line options	-Opa+, -Opa-
	Bit values	0, 1
Italic Courier New	A variable argument	file.o, where file can be any valid filename
0xnnnn	A hexadecimal number where n is a hexadecimal digit	0xFFFF, 0x007A
Square brackets [ ]	Optional arguments	mcc18 [options] file [options]
Curly brackets and pipe character: { | }	Choice of mutually exclusive arguments; an OR selection	errorlevel {0|1}
Ellipses...	Replaces repeated text	var_name [, var_name...]
	Represents code supplied by user	void main (void) { ... }

RECOMMENDED READING

This user's guide describes how to use the MCP402X Digital Potentiometer Evaluation Board. The following Microchip documents are available and recommended as supplemental reference resources.

MCP4011/2/3/4, "Low-Cost, 64-Step Volatile Digital POT in SOT-23" Data Sheet (DS21978).

MCP4021/2/3/4, "Low-Cost NV Digital POT in SOT-23 with WiperLock™ Technology" Data Sheet (DS21945).

PIC10F200/202/204/206, "6-Pin, 8-Bit Flash Microcontrollers" Data Sheet (DS41239)

Microchip provides online support via our web site at www.microchip.com. This web site is used as a means to make files and information easily available to customers. Accessible by using your favorite Internet browser, the web site contains the following information:

• Product Support – Data sheets and errata, application notes and sample programs, design resources, user's guides and hardware support documents, latest software releases and archived software
• General Technical Support – Frequently Asked Questions (FAQs), technical support requests, online discussion groups, Microchip consultant program member listing
• Business of Microchip – Product selector and ordering guides, latest Microchip press releases, listing of seminars and events, listings of Microchip sales offices, distributors and factory representatives

CUSTOMER SUPPORT

Users of Microchip products can receive assistance through several channels:

• Distributor or Representative
- Local Sales Office
• Field Application Engineer (FAE)
- Technical Support
• Development Systems Information Line

Customers should contact their distributor, representative or field application engineer (FAE) for support. Local sales offices are also available to help customers. A listing of sales offices and locations is included in the back of this document.

Technical support is available through the web site at: http://support.microchip.com

DOCUMENT REVISION HISTORY

Revision B (December 2005)

• Updated to include MCP401X devices
  • Enhancement of Operation Description
• Added Appendix C. "Using the BFMP Programmer to Power the Board" - Programming the MCP402X Digital Potentiometer Evaluation Board
• Added Appendix D. "Potential Programming Issue of the MCP402XEV"- A description of potential programming issues (and their solutions) with the MCP402X Digital Potentiometer Evaluation Board

Revision A (April 2005)

- Initial Release of this Document

NOTES:

Chapter 1. Product Overview

1.1 INTRODUCTION

This chapter provides an overview of the MCP402X Digital Potentiometer Evaluation Board and covers the following topics:

• What is the MCP402X Digital Potentiometer Evaluation Board?
• What the MCP402X Digital Potentiometer Evaluation Board includes

1.2 WHAT IS THE MCP402X DIGITAL POTENTIOMETER EVALUATION BOARD?

The MCP402X Digital Potentiometer Evaluation Board (MCP402XEV) allows the system designer to quickly evaluate the operation of Microchip Technology's MCP401X/2X Digital Potentiometer products.

The MCP402X Digital Potentiometer Evaluation Board PCB was designed to support:

• 8-pin, 150 mil SOIC MCP4021-XXX/SN devices
  • SOT-23-6 MCP4022-XXX/OT devices
  • SOT-23-6 MCP4023-XXX/OT devices
  • SOT-23-5 MCP4024-XXX/OT devices
  • 8-pin, 150 mil SOIC MCP4011-XXX/SN devices
  • SOT-23-6 MCP4012-XXX/OT devices
  • SOT-23-6 MCP4013-XXX/OT devices
  • SOT-23-5 MCP4014-XXX/OT devices

In addition to supporting the MCP401X/2X, the MCP402XEV also utilizes the SOT-23-6 PIC10F20X microcontroller.

The PIC10F20X is supplied with example firmware that debounces the INCR and DECR push buttons and generates the simple U/D protocol required by the MCP401X/2X to increment and decrement the potentiometer's wiper. It also generates the simple U/D protocol required by the MCP402X to lock and unlock the potentiometer's wiper.

1.3 WHAT THE MCP402X DIGITAL POTENTIOMETER EVALUATION BOARD KIT INCLUDES

This MCP402X Digital Potentiometer Evaluation Board Kit includes:

• One populated Printed Circuit Board (PCB)

- MCP4021-103/OT

- PIC10F206-I/OT with 00066_MCP402XEV.HEX programmed into memory

- Two push button switches: one for Increment commands (INCR), one for Decrement commands (DECR)

- Decoupling capacitors

- 5 resistors to isolate the switches and create a voltage divider with the MCP4021-103/OT

- One blank PCB to allow rapid prototyping of a specific digital potentiometer configuration

- 2 samples each of the MCP4021-202/OT, MCP4021-502/OT, MCP4021-103/OT and MCP4021-503/OT

• 1 PIC10F20X-I/OT sample

- MCP401X/2X Digital Potentiometer Evaluation Board User's Guide (electronic version on CD) (DS51546)

Chapter 2. Installation and Operation

2.1 INTRODUCTION

The MCP402X Digital Potentiometer Evaluation Board provides a tested, out-of-the-box example of a MCP401X/2X application. The circuit description is described in Section 2.2 "PCB Description", while the test and operating instructions are described in Section 2.3 "Test and Operating Instructions". A supplied blank PCB allows rapid prototyping of the designer's specific MCP401X/2X device, along with other desired passive components (resistor and capacitors) and connection posts.

2.2 PCB DESCRIPTION

The MCP402X Digital Potentiometer Evaluation Board has the following features:

• 150 mil, 8-pin SOIC pinout (U1) supports the MCP4021 and MCP4011 devices
• SOT-23-6 pinout (U2) supports the MCP4022/23/24 and MCP4012/13/14 devices
• SOT-23-6 pinout (U3) supports the PIC10F20X devices
• Connection terminals can be left unpopulated for easy connection using small alligator clip leads (clamped across the edge of the board) or populated with either through-hole or surface-mount terminals

- Footprints for optional passive components for:

• Power supply filtering
• Device bypass capacitor
• Terminal "A" pull-up resistor
• Terminal "B" pull-down resistor

- Footprints for two switches:

• INCR button operation can be detected by the PIC10F20X to generate Increment commands (move wiper toward terminal A)
• DECR button operation can be detected by the PIC10F20X to generate Decrement commands (move wiper toward terminal B)

- Button sequence instructions are printed on the back of the PCB

Appendix A.2 "Schematic" illustrates the schematic for the MCP402XEV.

Note: The PIC10F20X firmware (00066_MCP402XEV.HEX) must be programmed into the microcontroller before the MCP402XEV is functional.

2.2.1 Evaluating the MCP4021 and MCP4011

The MCP4021/11-XXXI/SN is an 8-pin digital potentiometer device with terminals A, B and W available on the device pins. Footprint U1 supports the 150 mil SOIC package. Resistors R2 and R3 are 2.5 kΩ on the populated PCB, along with the 10 kΩ MCP4021-103I/SN digital potentiometer. This creates a “windowed” voltage divider with a transfer function illustrated in Equation 2-1.

EQUATION 2-1: WINDOWED POTENTIOMETER – VOLTAGE DIVIDER CALCULATION

$$ V _ {w i p e r} = \frac {V _ {D D} R _ {w b} R 3 + (R 2 R 3 R + n o m)}{2 . 5 k 2 . 5 k 1 0 k} = \frac {5 . 0 V \cdot d / 1 0 k (\text {) } / \cdot \quad \text {无} k +}{2 . 5 k 2 . 5 k 1 0 k} $$

Where:

$$ d = \text { the wiper setting(0 to 63) } $$

Note 1: DO NOT populate U2 if using U1.

2: The MCP4011 has high-voltage tolerant pins and, therefore, accepts high-voltage Increment and Decrement commands. Since this device is nonvolatile, the WiperLock™ Technology feature is not present.

2.2.2 Evaluating the MCP4022 and MCP4012

The MCP4022/12-XXXI/OT is a 6-pin, stand-alone digital rheostat with terminals A and W available on the device pins. Footprint U2 supports the SOT-23-6 package. An "INCR" command moves the wiper toward terminal A, thus causing the resistance across the rheostat to decrease. A "DECR" command moves the wiper toward terminal B, thus causing the resistance across the rheostat to increase.

Note 1: DO NOT populate U1 if using U2.

2: The included MCP4021 digital potentiometer samples could be used to evaluate the MCP4022 simply by not populating R3 and letting terminal B float.

3: The MCP4012 has high-voltage tolerant pins and, therefore, accepts high-voltage Increment and Decrement commands. Since this device is nonvolatile, the WiperLock™ Technology feature is not present.

2.2.3 Evaluating the MCP4023 and MCP4013

The MCP4023/13-XXXI/OT is a 6-pin, grounded digital potentiometer with terminals A and W available on the device pins. Footprint U2 supports the SOT-23-6 package. Populating R2 will create a voltage divider with a transfer function illustrated in Equation 2-2.

EQUATION 2-2: GROUNDED POTENTIOMETER – VOLTAGE DIVIDER CALCULATION

$$ V _ {w i p e r} = \frac {V _ {D D} \cdot R _ {w b}}{R 2 + R _ {n o m}} = \frac {5 . 0 V d (1 0 k / 6 3)}{2 . 5 k 1 0 k +} $$

Where:

$$ d = \text { the wiper setting } (0 \text { to } 6 3) $$

Note 1: DO NOT populate U1 if using U2.

2: The included MCP4021 digital potentiometer samples could be used to evaluate the MCP4023 simply by shorting terminal B to GND.
3: The MCP4013 has high-voltage tolerant pins and, therefore, accepts high-voltage Increment and Decrement commands. Since this device is nonvolatile, the WiperLock™ Technology feature is not present.

2.2.4 Evaluating the MCP4024 and MCP4014

The MCP4024/14-xxxl/OT is a 5-pin, grounded digital rheostat with the W terminals available on the device pins. Footprint U2 supports the SOT-23-5 package. An "INCR" command moves the wiper toward terminal A, thus causing the resistance across the rheostat to increase. A "DECR" command moves the wiper toward terminal B, thus causing the resistance across the rheostat to decrease.

Note 1: DO NOT populate U1 if using U2.

2: The included MCP4021 digital potentiometer samples could be used to evaluate the MCP4024 simply by not populating R_2 , letting terminal A float and by shorting terminal B to GND.
3: The MCP4014 has high-voltage tolerant pins and, therefore, accepts high-voltage Increment and Decrement commands. Since this device is nonvolatile, the WiperLock™ Technology feature is not present.

2.3 TEST AND OPERATING INSTRUCTIONS

The populated PCB is configured to create a voltage divider from V_DD to V_SS using a 2.5 kΩ pull-up resistor (R2), the MCP4021-103I/SN (10 kΩ) and a 2.5 kΩ pull-down resistor (R3). To quickly evaluate the digital potentiometer's performance, the following test equipment is required:

• 2.7V to 5.5V power supply
• Voltmeter or Digital Multimeter (DMM)

Figure 2-1 shows the Digital Potentiometer Evaluation Board PCB, components and the connection points that will be used in the step-by-step demonstration.

Increment (INCR) Switch J1 R5 U/D CS 102-00066 GND Resistor R2 (A to VDD) Baseline Flash MCU Programmer (BFMP) Interface Resistor R3 (B to GND) Decrement (DECR) Switch DEC8 A B W Digital Potentiometer Node A Pad Digital Potentiometer Node B Pad Digital Potentiometer Wiper W Pad

FIGURE 2-1: Digital Potentiometer Evaluation Board Overview.

2.3.1 Test Setup

1. Connect the power supply “+” to VDD and the “−” to GND.
2. Connect the voltmeter to the W terminal and GND.

The voltmeter should reflect the wiper setting with respect to Equation 2-3.

EQUATION 2-3: POPULATED PCB – VOLTAGE DIVIDER CALCULATION

$$ V _ {w i p e r} = \frac {V _ {D D} R _ {w b} R 3 + (R 2 R 3 R + _ {A B})}{2 . 5 k + 2 . 5 k 1 0 k} = \frac {5 . 0 V \cdot d (1 0 k) / \cdot + 2 . 5 k)}{2 . 5 k + 2 . 5 k 1 0 k} $$

Where:

$$ d = \text { the wiper setting } (0 \text { to } 6 3) $$

Using R2 and R3 = 2.5 kΩ:

• If a 2 kΩ MCP4021 is utilized, the output range will be approximately 1.79V to 3.21V.
• If a 5 kΩ MCP4021 is utilized, the output range will be approximately 1.25V to 3.75V.
• If a 10 kΩ MCP4021 is utilized, the output range will be approximately 0.83V to 4.17V.
• If a 50 kΩ MCP4021 is utilized, the output range will be approximately 0.23V to 4.77V.

2.3.2 MCP402X Digital Potentiometer Evaluation Board Firmware Operation

The 00066_MCP402XEV .HEX firmware programmed into the PIC10F20X provides a very simple interface to operate the MCP402X digital potentiometer. There are ten basic commands supported for the user to exercise the MCP402X digital potentiometer.

Table 2-1 shows the firmware commands of the Digital Potentiometer Evaluation Board.

TABLE 2-1: DIGITAL POTENTIOMETER EVALUATION BOARD FIRMWARE INCREMENT/DECREMENT COMMANDS

Command Button Sequence

#

Increment/Decrement - (Low Voltage/High Voltage)

# of Steps

Saves Wiper Value in EEPROM

High Voltage on CS and U/D pins?

After Command Wiper is

Works when Wiper is “locked”

MCP401x will INCR/DECR

#1 (Depress) ^(5)

#2 (Depress) ^(5)

#3 (Release)

#4 (Release)

“locked”

“ unlocked”

1 INCR - (Low Voltage) 1

^(1)

Yes

No

—

—

No

Yes

INCR (for < 2 sec)

—

—

—

—

2 INCR - (High Voltage) ^(6)

1^(1)

Yes

Yes

—

Yes

Yes

Yes

INCR (for < 2 sec)

DECREMENT (for < 2 sec)

INCR

DECR

DECR

3 INCR - (High Voltage) ^(6)

1^(1)

Yes

Yes

Yes

—

Yes

Yes

INCR (for < 2 sec)

DECREMENT (for < 2 sec)

DECR

INCR

INCR

4 INCR - (Low Voltage)

64^(2)

Yes

No

—

—

No

Yes

INCR (for > 2 sec)

—

—

—

—

5 INCR - (High Voltage) ^(6)

64^(2)

Yes

Yes

—

Yes

Yes

Yes

INCR (for < 2 sec)

DECREMENT (for > 2 sec)

INCR

DECR

DECR

6 DECR - (Low Voltage) 1

^(3)

Yes

No

—

—

No

Yes

DECR (for < 2 sec)

—

—

—

—

7 DECR - (High Voltage) ^(6)

1^(3)

Yes

Yes

—

Yes

Yes

Yes

DECR (for < 2 sec)

INCR (for < 2 sec)

DECR

INCR

INCR

8 DECR - (High Voltage) ^(6)

1^(3)

Yes

Yes

Yes

—

Yes

Yes

DECR (for < 2 sec)

INCR (for < 2 sec)

INCR

DECR

DECR

9 DECR - (Low Voltage)

64^(4)

Yes

No

—

—

No

Yes

DECR (for > 2 sec)

—

—

—

—

10 DECR - (High Voltage) ^(6)

64^(4)

Yes

Yes

—

Yes

Yes

Yes

DECR (for < 2 sec)

INCR (for > 2 sec)

DECR

INCR

INCR

Note 1: Move wiper W towards node A (Increment wiper 1 step).
2: Move wiper W to node A (Increment wiper 64 steps). Forces the wiper setting to "full-scale" (wiper W = node A).
3: Move wiper W towards node B (Decrement wiper 1 step).
4: Move wiper W to node B (Decrement wiper 64 steps). Forces the wiper setting to "zero scale" (wiper W = node B).
If there is more than one sequence, the button sequence #1 must continue to be held down while progressing to sequence #2. Example: Command # 2 requires the INCR button to be depressed. Then, before 2 seconds elapses, the DECR button must be depressed. Next, before 2 seconds elapses, the INCR button must be released. The DECR button can then be released.
6: High-voltage commands require a system voltage ( V_DD ) greater than 5.0V to allow the simple charge pump to generate the V_IHH MIN voltage for the pin.

2.3.3 Running the Ratiometric Voltage Demo

Table 2-2 provides step-by-step instructions to perform a demonstration of the MCP402X Digital Potentiometer Evaluation Board. Measuring Ratiometric Voltage

TABLE 2-2: MEASURING RATIOMETRIC VOLTAGE

Step	Action Result
1 Power	er up the populated Digital Potentiometer Evaluation Board.Voltage calculations use a system voltage of 5V.	—
	Board can be powered via a valid voltage (such as 5V) on the VDD and GND PCB Pads, or by connecting a BFMP programmer that is connected to an active PC's USB port (powered via the USB connection).
2 Set	DMM to measure the required voltage range (0V to 5.5V).Connect the DMM ground connection to the evaluation board GND terminal and the DMM V/Ω connection to terminal W of the evaluation board.	—
3 Turn	on DMM. On DMM:	DMM will display the voltage determined by the current non-volatile setting of the wiper.
4 On	the Digital Potentiometer Evaluation Board: Implement Command #5 (see Table 2-1).	On the Digital Potentiometer Evaluation Board: WiperLockTM Technology is disabled and the wiper is incremented from power-on position.
		On DMM:Voltage increments approximately 0.05V.
5 On	the Digital Potentiometer Evaluation Board: Implement Command #4 (see Table 2-1).	On the Digital Potentiometer Evaluation Board: Wiper is forced to the full-scale position (Wiper W = node A).
		On DMM:Voltage equals approximately 4.17V.
6 On	the Digital Potentiometer Evaluation Board: Implement Command #6 (see Table 2-1).	On the Digital Potentiometer Evaluation Board: Wiper is decremented one position from the full-scale position.
		On DMM:Voltage equals approximately 4.12V.
7 On	the Digital Potentiometer Evaluation Board: Implement Command #6 (see Table 2-1) 15 more times.	On the Digital Potentiometer Evaluation Board: Wiper is decremented to the 25% position from node A (full-scale) to node B (zero-scale).
		On DMM:Voltage equals approximately 3.33V.
8 On	the Digital Potentiometer Evaluation Board: Turn off/disconnect power supply.	On DMM:Voltage equals approximately 0V.
9 On	the Digital Potentiometer Evaluation Board: Reapply power to Digital Potentiometer Evaluation Board.	On DMM:Voltage equals approximately 3.33V. This shows that the MCP4021 retained the last selected wiper setting.
10 On	the Digital Potentiometer Evaluation Board: Implement Command #3 (see Table 2-1).	On the Digital Potentiometer Evaluation Board: Wiper is incremented one position and the wiper is locked (WiperLock Technology is enabled).
		On DMM:Voltage equals approximately 3.38V.
11 On	the Digital Potentiometer Evaluation Board: Implement Command #1 (see Table 2-1).	On the Digital Potentiometer Evaluation Board: Wiper is NOT moved due to the wiper being locked (WiperLockTM Technology is enabled).
		On DMM: Voltage equals approximately 3.38V.
12 On	the Digital Potentiometer Evaluation Board: Turn off/disconnect power supply.	On DMM: Voltage equals approximately 0V.
13 On	the Digital Potentiometer Evaluation Board: Re-apply power to Digital Potentiometer Evaluation Board.	On DMM: Voltage equals approximately 3.38V. This shows that the MCP4021 retained the last saved wiper setting.

2.3.4 Wiper Voltages

Table 2-3 shows the relation between the wiper position and the voltage on the wiper when 5.0 volts is applied to the MCP402X Digital Potentiometer Evaluation Board where the resistors R2 and R3 are 2500Ω and the MCP4011 resistor value ( R_AB ) is 10 kΩ. Equation 2-4 shows the formula for these calculations.

EQUATION 2-4: CALCULATING THE VOLTAGE ON THE MCP402X DIGITAL POTENTIOMETER EVALUATION BOARD

$$ \text { Voltage at Wiper } = \text { System } V _ {D D} \bullet \frac {(R 3 + (\text { Wiper Position } \bullet (R _ {A B}) / 6 3))}{R 3 + R _ {A B} + R 2} $$

Where:

$$ \text { System } V _ {\mathrm{DD}} = 5. 0 \mathrm{V} $$

$$ R 2 = 2. 5 \mathrm{k} \Omega $$

$$ R 3 = 2. 5 \mathrm{k} \Omega $$

$$ R _ {A B} = 1 0 k \Omega $$

The typical step resistance for the 10 kΩ MCP4021 is approximately 158.73Ω. With a 5V supply and a 15 kΩ total resistance (2.5 kΩ + 2.5 kΩ + 10 kΩ), the delta voltage per step is approximately 0.053V.

TABLE 2-3: WIPER POSITION AND CORRESPONDING VOLTAGE

Wiper Wiper		Wiper Wiper
Position	Voltage (V)					Position	Voltage (V)		Position	Voltage (V)
00^(1)	0.833		16	1.680	32	2.52	648		3.373
01	0.86617	1.7	33332.57	9493.42	6
02	0.93918	1.7	86342.63	2503.47	9
03	0.99219	1.8	39352.68	5513.53	2
04	1.04520	1.8	92362.73	8523.58	5
05	1.09821	1.9	44372.79	1533.63	8
06	1.15122	1.9	97382.84	4543.69	0
07	1.20423	2.0	50392.89	7553.74	3
08	1.25724	2.1	03402.95	0563.79	6
09	1.31025	2.1	56413.00	3573.84	9
10	1.36226	2.2	09423.05	6583.90	2
11	1.41527	2.2	62433.10	8593.95	5
12	1.46828	2.3	15443.16	1604.00	8
13	1.52129	2.3	68453.21	4614.06	1
14	1.57430	2.4	21463.26	7624.11	4
15	1.62731	2.4	74473.32	0	63				(2)	4.167

Note 1: This is zero-scale, wiper is connected to terminal B.
2: This is full-scale, wiper is connected to terminal A.

2.4 FIRMWARE DESCRIPTION

The 000066_MCP402XEV.ASM source code was written using assembly language for the PIC10F206 microcontroller. Refer to Appendix E. "00066_MCP402XEV.ASM Source Code". The firmware initializes its I/O so that it can poll the INCR and DECR buttons every millisecond. If the button has been depressed for 40 out of 50 ms, it is considered to be debounced and asserted. The button state is used to determine if a new "Action State" is desired. This simple state machine then decodes the desired action. Once the desired command has been determined, a subroutine that performs the desired command is executed. The low-voltage commands are driven directly from the PIC10F206 I/O, but the high-voltage commands require some additional hardware to generate the required 8V signal.

When a high-voltage command is required, the PIC10F206's unique OSCOUT feature is utilized. The OSCOUT function allows the instruction clock to be driven on GP2/OSCOUT under software control. A simple charge pump consisting of 2 – 0.01 F capacitors and a BAV99 dual diode is constructed as seen in Appendix

A.2 "Schematic". When the OSCOUT is enabled, a 1 MHz clock drives the charge pump that produces an 8.4V signal on the MCP401X/2X's CS pin (assuming V_DD = 5.0V ). Utilizing such a charge pump requires special attention to the timing of the CS & U/D signals.

Refer to the comments in the 00066_MCP402XEV.ASM source code for more details on the firmware's operation. Refer to Appendix E. "00066_MCP402XEV.ASM Source Code".

NOTES:

Appendix A. Schematic and Layouts

A.1 INTRODUCTION

This appendix contains the following schematics and layout diagrams for the MCP402X Digital Potentiometer Evaluation Board.

• Schematic – Shows the schematic of the MCP402X Digital Potentiometer Evaluation Board. The populated PCB was built using this schematic.
• Board Layout – Top Layer + Silk-screen
• Board Layout – Top Silk-Screen
• Board Layout – Bottom Layer + Silk-screen
• Board Layout – Bottom Layer

A.2 SCHEMATIC

Rev Description Date 1 J1 N/C INR Expense SEL Expense VDD HDR1X6 DECR 2.5K R4 CS U/D U2 6 A 2 Vss 3 U/D C4 8.1uF MCP4822/23/24 VDD R2 2.5K A INCR 2.5K R5 U3 GP8 GP3/MCLR 6 2 Vss VDD 5 GP1 GP2 PIC10F286 VDD U1 1 Vdd U/D B 2 Vss NC 7 3 A B 6 4 W CS 5 MCP4821 7.5K RE C3 8.81uF SE Expense D1 BAV99 C1 8.81uF C2 8.81uF B W B R3 2.5K GND Title MCP402X Digi Pot Eval Board Size 105-00066 Rev 1 B MICROCHIP Date: Fri Mar 18, 2005 Eng:im Simons Drawn by: J.Garcio Sheet 1 of 1 A B C D C D

A.3 MCP402X BOARD LAYOUT - TOP LAYER + SILK-SCREEN

INCR J1 R5 U/D CS 102-00066 GND C3 R2 C4 U2 VDD 2n C1 F1 R4 D1 C2 DECR A B W

A.4 MCP402X BOARD LAYOUT - BOTTOM LAYER

Pure electrical circuit lines without any symbols

A.5 MCP402X BOARD LAYOUT - TOP SILK-SCREEN

102-00066 GND INCR J1 R5 U/D CS C3 £N C1 R1 D1 C2 R4 U1 R2 U2 R3 VDD DECR A B W

A.6 MCP402X BOARD LAYOUT - BOTTOM LAYER + SILK-SCREEN

+." = Boolean Button & . -." = Release Button INC+ +YCIN1 VJ = -YCIN1, +YCIN1 INC+ , INC- = VA 1ucl ucl ucl DEC+ , DEC- = VA 2d clemt INC+ +YCIN1 VJ +A d = b04 VJ 1ucl ucl ucl DEC+ +YCIN1 VJ +A d = b04 VJ 2d clemt DEC+ +YCIN1 VJ +A d = b04 VJ 3d clemt (MT)Xcdoqiv w o \w 1ucl VH= -YCIN1,-YCIN1,+YCIN1,+YCIN1 (MT)Xcdoqiv w o \w 1ucl VH= -YCIN1,-YCIN1,+YCIN1,+YCIN1,+YCIN1 (MT)Xcdoqiv w o \w 1ucl VH= -YCIN1,-YCIN1,+YCIN1,+YCIN1,+YCIN1 (MT)Xcdoqiv w o \w 1ucl VH= -YCIN1,-YCIN1,+YCIN1,+YCIN1,+Ycdoqiv W (MT)Xcdoqiv w o \w 1ucl VH= -YCIN1,-YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,+YCIN1,

Appendix B. Bill Of Materials (BOM)

TABLE B-1: BILL OF MATERIALS

Qty	Reference Description	Manufacturer Part Number
2 C1,C2,C3 Cap 0.01 μF		50V CERAMICX7R 0805	Kemet®	C0805C103K5RACTU
1 C4	Cap .1 μF 25V CERAMICX7R 0805		Panasonic® Corporation – ECG	ECJ-2VB1E104K
1 D1	Dual Diode, SOT-23-3,May substitute withFairchild® BAV99		ON Semiconductor®	BAV99LT1
2 INCR, DECR Switch LT		Touch 6X3.5100 GF SMD	Panasonic Corporation – ECG	EVQ-PJS04K
1 J1	Conn Header 6pos .100 VERT TIN(Optional)		Molex®/Waldom®Electronics Corp	22-28-4061
1	R1	Res 7.5 kΩ 1/10W 1%0805 SMD	Panasonic Corporation – ECG	ERJ-6ENF5111V
2	R2,R3	Res 2.5 kΩ 1/10W 1%0805 SMD	Panasonic Corporation – ECG	ERJ-6ENF5111V
2	R4,R5	Res 2.5 kΩ 1/10W 1%0805 SMD	Panasonic Corporation – ECG	ERJ-6ENF5111V
1 U1	MCP4021-103/SN 10 kΩDigital Potentiometer		Microchip Technology Inc.	MCP4021-103/SN
1 U3	PIC10F206, 6-Pin,8-Bit Flash Microcontrollers		Microchip Technology Inc.	PIC10F206-I/OT
1 U2	MCP4022/23/24 5/6 Pin DigitalPotentiometer (Optional)		Microchip Technology Inc.	MCP4024-502/OT
7 A,B	W,VDD,GND,U/D,CS	Test Point PC Compact SMT(Optional)	Keystone® Electronics	5016

NOTES:

Appendix C. Using the BFMP Programmer to Power the Board

C.1 POWERING THE BOARD USING THE BFMP PROGRAMMER

The BFMP programmer (PG164101) uses a 6-pin interface for programming. The PICkit™ 2 Flash Starter Kit (PG164120 or DV164120) uses the same interface.

The MCP402X Digital Potentiometer Evaluation Board (MCP402XEV) plugs into the BFMP (or PICkit™ 2 Flash Starter Kit) in the orientation shown in Figure C-1.

USB Cable to PC BFMP Header connector BFMP Board (Top-side) MCP402XEV Board (Bottom-side) Pin #1 Pin #1

FIGURE C-1: BFMP Hardware and MCP402X Digital Potentiometer Evaluation Board.

These programmers use the PICkit™ 1 Baseline Flash Programmer software. This GUI should be configured as shown in Figure C-2. Selecting Device Power causes the BFMP to power the attached board all the time (not just during programming). This allows the MCP402X Digital Potentiometer Evaluation Board to be easily demonstrated without needing to carry a power supply (although a DMM is still required).

PICkit(tm) 1 Baseline Flash Programmer File Programmer Tools About Program Memory 000 FFFF FFFF FFFF FFFF FFFF FFFF FFFF 008 FFFF FFFF FFFF FFFF FFFF FFFF FFFF 010 FFFF FFFF FFFF FFFF FFFF FFFF FFFF 018 FFFF FFFF FFFF FFFF FFFF FFFF FFFF 020 FFFF FFFF FFFF FFFF FFFF FFFF FFFF 028 FFFF FFFF FFFF FFFF FFFF FFFF FFFF 030 FFFF FFFF FFFF FFFF FFFF FFFF FFFF 038 FFFF FFFF FFFF FFFF FFFF FFFF FFFF 040 FFFF FFFF FFFF FFFF FFFF FFFF FFFF 048 FFFF FFFF FFFF FFFF FFFF FFFF FFFF 050 FFFF FFFF FFFF FFFF FFFF FFFF FFFF 058 FFFF FFFF FFFF FFFF FFFF FFFF 060 FFFF FFFF FFFF FFFF FFFF FFFF 068 FFFF FFFF FFFF FFFF FFFF Board Controls ✓ Device Power □ 2.5 kHz Osc Read Device Write Device Verify Erase Quit Device Configuration Device PIC10F206 Configuration Word 0xFFFF User IDs CheckSum 0xEE1D OSCCAL 0xFFFF Firmware Version: 2.0.2 Select PIC10F206 Ensure Device Power IS checked and 2.5 kHz Osc is NOT checked.

FIGURE C-2: PICkit™ 1 Baseline Flash Programmer - Configuration #2.

Note: When programming the MCP402X Digital Potentiometer Evaluation Board, under "Board Controls", DO NOT check Device Power. This ensures that the PIC10F206 is only powered during the programming cycle.

Appendix D. Potential Programming Issue of the MCP402XEV

D.1 INTRODUCTION

When programming the MCP402XEV with a Microchip programmer (such as the BPMF or MPLAB ^® ICD 2), the PIC10F206 may not program correctly due to the load on the ICSPDAT pin. This issue relates to PCBs marked 104-00066 and 104-00066R2.

Due to the current path to ground that is present with the D1 and R1 components through capacitor C2, the programming voltage on the ICSPDAT signal may not meet the voltage requirements of the PIC10F206 GP1 pin.

To address this when programming the board, lift up one of the terminals of capacitor C2 (see Figure D-1). This will stop the ICSPDAT signal voltage from being loaded down while capacitor C2 is charging. The schematic is shown in Figure D-2.

After programming, capacitor C2 must be reconnected to the circuit. This is because this circuit generates the high voltage for the high voltage commands.

102-00066 GND INCR J1 R5 U/D CS This capacitor connection needs to be opened for programming. After programming has been completed, this capacitor needs to be reconnected in the circuit. Lift this end C3 R2 C4 U2 C1 R1 R4 VDD D1 C2 DECR A B W

FIGURE D-1: MCP402XEV R2 PCB Layout – ECN #1.

Rev Description Date 1 2 3 4 A B C D 1 2 3 4 J1 9X130H VCC u8_cspnux R5_cspnux u0 vW DECR INCR C2 JP1 This is the node that needs to be open when programming. PC18F286 U3 GP0 GP3/VCUR VDD GP1 GP2 VDD U1 C3 0.81µF C1 0.81µF D1 BAV99 C2 0.81µF U/D U2 Vdd A 6 A Vss W 5 S U/D CS 4 S MCP4022/23/24 C4 0.1µF R2 2.5K A VDD Vcc 1 Vdd U/D B 7 wB_cspnux Vss Vss NC 6 S A B 5 S MCP4821 R3 2.5K GND This is the node that needs to be open when programming. C2 0.81µF A B C D Microchip Eng:Jim Simons Date: Fri Mar 18, 2005 Drawn by: J.Garcia Sheet 1 of 1 Title MCP402X Digi Pot Eval Board Size B 105-00066 Rev 1 Microchip Filename:103-00066 MCP402XEV v100.sch

FIGURE D-2: MCP402XEV R2 Schematic PCB R2, ECN #1.

Appendix E. 00066\_MCP402XEV.ASM Source Code

E.1 INTRODUCTION

This appendix documents the example PIC10F20X source code used on the populated PCB. The source code is described in detail by the comments within the.ASM file. The 00066_MCP402XEV.ASM, PIC10F206.INC and MCP402XEV.HEX files can be found on the Microchip web site (www.microchip.com) and on the included CD.

Software License Agreement

The software supplied herewith by Microchip Technology Incorporated (the "Company") is intended and supplied to you, the Company's customer, for use solely and exclusively with products manufactured by the Company.

The software is owned by the Company and/or its supplier, and is protected under applicable copyright laws. All rights are reserved. Any use in violation of the foregoing restrictions may subject the user to criminal sanctions under applicable laws, as well as to civil liability for the breach of the terms and conditions of this license.

THIS SOFTWARE IS PROVIDED IN AN "AS IS" CONDITION. NO WARRANTIES, WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. THE COMPANY SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE

TITLE "MCP402XEV Firmware"
;*****
; Author: Jim Simons
; Tools: MPLAB(r) 7.10 using MPLINK(tm)
; Editor: ComicSans 8pt w/8 character Tabs
; Files: 00066_MCP402XEV.asm
; p10f206.inc
;
; Description: Exercise the MCP402x devices using the MCP402x EV board.
; Simply use the INCR & DECR buttons to execute the INCR & DECR serial commands.
;
; Serial Commands Action State
;
; LV Increment w/EE Depress UP, Release UP LVwEE = 1 3
; LV Decrement w/EE Depress DOWN, Release DOWN LVwEE = 1 4
; LV Increment w/o EE Depress UP, Release UP LVwEE = x 3
; LV Decrement w/o EE Depress DOWN, Release DOWN LVwEE = x 4
; LV 64 Increments Depress UP, Hold for 2s, Release UP 1
; LV 64 Decrements Depress DOWN, Hold for 2s, Release DOWN 2
; HV Incr w/o WL Depress UP, Depress DOWN, Release UP, Release DOWN 11
; HV Decr w/o WL Depress DOWN, Depress UP, Release DOWN, Release UP 12
; HV 64 Incr w/o WL Depress UP, Depress DOWN, Hold for 2s, Release UP, Release DOWN 5
; HV 64 Decr w/o WL Depress DOWN, Depress UP, Hold for 2s, Release DOWN, Release UP 6
; HV Incr w/WL Depress UP, Depress DOWN, Release DOWN, Release UP 13
; HV Decr w/WL Depress DOWN, Depress UP, Release UP, Release DOWN 14 

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE (CONTINUED)
;**** ; Connections/Schematic ;*** ; ; MCP pin MCP4021 MCP4022 MCP4023 MCP4024 ; ; 1 Vdd Vdd Vdd Vdd ; 2 Vss Vss Vss Vss ; 3 A U/D U/D U/D ; 4 W CS CS CS ; 5 CS W W W ; 6 B A A - ; 7 - - - - ; 8 U/D - - - ; ; MCP402x PIC10F206 Ext Components ; ; Vdd Vdd 0.1uF - Vss ; Vss Vss - ; A - 2.5k - Vdd ; W - - ; B - 2.5k - Vss ; CS GP0/ICSPDAT (int pu) 2.5k - DECR - Vss, 7.5k - CS & BAV99 ; U/D GP1/ICSPCLK (int pu) 2.5k - INCR - Vss ; - GP2/OSCOUT 0.01uF - BAV99 - 0.01uF - Vss ; - GP3/Vpp (int pu) optional SW or Jumper put on BFMP header pins 4 & 6 ; ;*** ; Assemble Time Variables SaveWiper equ 1 ; comment this line prevent LV commands from Saving the Wiper ; ;*** ; Configure the PIC ;******* list p=10F206 ; list directive to define processor

include ; processor specific variable definitions

__CONFIG _MCLRE_OFF & _CP_OFF & _WDT_ON ERRORLEVEL -302

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE (CONTINUED)
;* General Pupose Register Definitions ;* GPRS UDATA State res 1 ; variable to track the "state" value ; this code functions as a state machine ; bits 3:0 stores the state 0-15 indicator ; bits 7:6 stores the debounced button states OldState res 1 ; allows program to see if State changed Exit res 1 ; variable to count the number ms to test for a button press DebounceUP res 1 ; variable to count the number of ms UP was pressed DebounceDOWN res 1 ; variable to count the number of ms DOWN was pressed DLYCNT1 res 1 ; variable for the delay subroutines DLYCNT2 res 1 ; variable for the delay subroutines

define UD GPIO,1 ; GP1 tied to UD & has "INCR" switch connected via 2.2k resistor

define CS GPIO,0 ; GP0 tied to CS & has "DECR" switch connected via 2.2k resistor

define UP GPIO,1 ; Momentary switch UP

define DOWN GPIO,0 ; Momentary switch DOWN

define CP GPIO,2 ; OSCOUT pin for Charge Pump

define PowerDown GPIO,3 ; Vpp for programming & PowerDown input to put uC to SLEEP

define HV_CS OSCCAL,FOSC4 ; Drives CS to HVDD (drive CS high first)

define UP_State State,7 ; Debounced UP State - using bits 5:4 are critical

define DOWN_State State,6 ; Debounced DOWN State - using bits 5:4 are critical

;* Reset Code ;* RESET CODE ; processor reset vector + 1 ;ResetVector ; Device resets to 0x1FF to get the factory calibration goto Start ; Lower half of memory reserved for subroutines

;* Main Code ;* MAIN CODE Start Init_Oscillator ; Internal RC calibration value is placed at location 0xFF by Microchip ; as a movlw k, where the k is a literal value. movwf OSCCAL ; update register with factory cal value bcf OSCCAL,FOSC4 ; make sure the FOSC4 is disabled to shut charge pump off

StateMachineReset movlw b'11110011' ; Disable the Comparator & make inputs digital movwf CMCON0 bcf CMCON0, CMPON ; needs to be on to get GP2 as a General Purpose Output movlw b'10011010' ; disable Wake-Up on Pin Change, ; enable weak pullups for button inputs ; TOCS must be 0 for GP2 TRIS to be active ; set up for 72ms WDT

option

Init clrf State clrf OldState call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE (CONTINUED)

ButtonCheck ; Debounce Buttons
btfss PowerDown ; If pulled low, put uC to SLEEP
goto LowPowerMode
bsf UP_State
bsf DOWN_State ; initialize Button_State to indicate no button pressed
movlw .50 ; debounce the buttosns for 50mS to see if pressed
movwf Exit
movlw .40 ; if pushed for 40 of 50 tests, then valid UP
movwf DebounceUP
movwf DebounceDOWN

DebounceLoop
call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled)
movlw .99
call VAR5TcyDELAY ; 5 + (99*5) = 500us
btfss UP
decfsz DebounceUP,f
goto CheckDOWN
bcf UP_State ; UP Button Pressed

CheckDOWN
call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled)
movlw .99
call VAR5TcyDELAY ; 5 + (99*5) = 500us
btfss DOWN
decfsz DebounceDOWN,f
goto DebounceLoopTest
bcf DOWN_State ; DOWN Button Pressed

DebounceLoopTest
decfsz Exit,f
goto DebounceLoop

call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands
movf State,w
call DetermineState ; subroutine to determine the next state
movwf State
xorwf OldState,w
btfss STATUS,Z
call PerformState ;State changed, now do something
movlw .5
call VAR1000TcyDELAY ; Make sure EE Write Cycle has finished
movf State,w
movwf OldState
goto ButtonCheck ; Loop for button presses

;*******************************
; State Machine Code
;*******************************
; State0 goto StateMachineReset ; State 0, no action, shouldn't get here

Statel ; UP button pressed
movlw .200 ; 200x10mS = 2s
movwf Exit 

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE (CONTINUED)

Loop1_2sec
    call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled)
    movlw .5 ; 5ms delay
    call VAR1000TcyDELAY
    btfss DOWN ; if DOWN gets pressed, exit
    retlw .1
    call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled)
    movlw .5 ; 5ms delay
    call VAR1000TcyDELAY
    btfsc UP ; if UP gets released, exit
    retlw .1
    decfsz Exit,f
    goto Loop1_2sec
    call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands
    movlw .64
    call LV_Increment
    ; movlw .4
    ; call VAR1000TcyDELAY ; add a 4mS delay for E/W cycle
    call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled)
LV_IncrExit
    clrwdt
    btfss UP ; if UP gets released, exit
    goto LV_IncrExit
    clrf State
    retlw .1
State2 ; DOWN button pressed
    movlw .200 ; 200x10mS = 2s
    movwf Exit
Loop2_2sec
    call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled)
    movlw .5 ; 5ms delay
    call VAR1000TcyDELAY
    btfss UP ; if UP gets pressed, exit
    retlw .2
    call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled)
    movlw .5 ; 5ms delay
    call VAR1000TcyDELAY
    btfsc DOWN ; if DOWN gets released, exit
    retlw .2
    decfsz Exit,f
    goto Loop2_2sec
    call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands
undesired U/D commands
    movlw .64
    call LV_Decrement
; movlw .4
; call VAR1000TcyDELAY ; add a 4mS delay for E/W cycle
    call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled)
LV_DecrExit
    clrwdt
    btfss DOWN ; if DOWN gets released, exit
    goto LV_DecrExit
    clrf State
    retlw .2
State3 ; LV Increment
    call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands
    movlw .1
    call LV_Increment
    clrf State
    retlw .3 

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE (CONTINUED)

State4 ; LV Decrement
call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands
movlw .1
call LV_Decrement
clrf State
retlw .4
State5 ; Both buttons pressed
movlw .200 ; 200x10mS = 2s
movwf Exit
Loop5_2sec
call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled)
movlw .5 ; 5ms delay
call VAR1000TcyDELAY
btfsc UP ; if UP gets released, exit
retlw .5
call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled)
movlw .5 ; 5ms delay
call VAR1000TcyDELAY
btfsc DOWN ; if DOWN gets released, exit
retlw .5
decfsz Exit,f
goto Loop5_2sec
call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands
movlw .64
call HV_Increment_WL_Disable
; movlw .4
; call VAR1000TcyDELAY ; add a 4mS delay for E/W cycle
HV_IncrExit clrwdt
call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled)
movlw .10
call VAR1000TcyDELAY ; add a 10mS delay for settling time
btfss DOWN ; if DOWN gets released, exit
goto HV_IncrExit
call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled)
movlw .10
call VAR1000TcyDELAY ; add a 10mS delay for settling time
btfss UP ; if UP gets released, exit
goto HV_IncrExit
clrf State
retlw .5
State6
movlw .200 ; 200x10mS = 2s
movwf Exit
Loop6_2sec
call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled)
movlw .5 ; 5ms delay
call VAR1000TcyDELAY
btfsc UP ; if UP gets released, exit
retlw .6
call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled)
movlw .5 ; 5ms delay
call VAR1000TcyDELAY
btfsc DOWN ; if DOWN gets released, exit
retlw .6
decfsz Exit,f
goto Loop6_2sec
call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands
movlw .64
call HV_Decrement_WL_Disable
; movlw .4
; call VAR1000TcyDELAY ; add a 4mS delay for E/W cycle 

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE (CONTINUED)

HV_DecrExit clrwdt
    call GPIO_TestUP ; make GP1/INCR/UD an input (w/pu enabled)
    movlw .10
    call VAR1000TcyDELAY ; add a 10mS delay for settling time
    btfss UP ; if UP gets released, exit
    goto HV_DecrExit
    call GPIO_TestDOWN ; make GP0/DECR/CS an input (w/pu enabled)
    movlw .10
    call VAR1000TcyDELAY ; add a 10mS delay for settling time
    btfss DOWN ; if DOWN gets released, exit
    goto HV_DecrExit
    clrf State
    retlw .6

State7
State8
State9
State10
State11 ; HV Increment w/o WL
    call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands
    movlw .1
    call HV_Increment_WL_Disable
    clrf State
    retlw .11

State12 ; HV Increment w/o WL
    call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands
    movlw .1
    call HV_Decrement_WL_Disable
    clrf State
    retlw .12

State13 ; HV Decrement w/WL
    call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands
    call HV_Increment_WL_Enable
    clrf State
    retlw .13

State14 ; HV Decrement w/WL
    call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands
    call HV_Decrement_WL_Enable
    clrf State
    retlw .14

State15
    goto StateMachineReset

;*******************************
; Low Power Mode
;*******************************
LowPowerMode
movlw b'11111000' ; make all I/O pins an output
tris GPIO
movlw b'1111111'
movwf GPIO ; output high
movlw b'1001111' ; disable Wake-Up on Pin Change,
; enable weak pullups for button inputs
; TOCS must be 0 for GP2 TRIS to be active
; set up for 2.3ms WDT
option
sleep ; put into lowest power setting
goto Start ; shouldn't get here

SUBS CODE 

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE (CONTINUED)
; Statement ; State Machine Subroutines ; Statement DetermineState swapf State,f rrf State,f rrf State,w andlw b'0011111'; mask invalid states addwf PCL,f S0_00 retlw .0 ; both buttons pressed at same time, shouldn't be here S0_01 retlw .1 ; UP button pressed, change state S0_10 retlw .2 ; DOWN button pressed, change state S0_11 retlw .0 ; no change S1_00 retlw .5 ; both buttons pressed, change state S1_01 retlw .1 ; no change S1_10 retlw .0 ; shouldn't be here, reset state S1_11 retlw .3 ; UP button released, change state S2_00 retlw .6 ; both buttons pressed, change state S2_01 retlw .0 ; shouldn't be here, reset state S2_10 retlw .2 ; no change S2_11 retlw .4 ; DOWN button released, change state S3_00 retlw .0 ; shouldn't be here, reset state S3_01 retlw .0 ; shouldn't be here, reset state S3_10 retlw .0 ; shouldn't be here, reset state S3_11 retlw .0 ; shouldn't be here, reset state S4_00 retlw .0 ; shouldn't be here, reset state S4_01 retlw .0 ; shouldn't be here, reset state S4_10 retlw .0 ; shouldn't be here, reset state S4_11 retlw .0 ; shouldn't be here, reset state S5_00 retlw .5 ; no change S5_01 retlw .7 ; DOWN button released, change state S5_10 retlw .9 ; UP button released, change state S5_11 retlw .0 ; shouldn't be here, reset state S6_00 retlw .6 ; no change S6_01 retlw .10 ; DOWN button released S6_10 retlw .8 ; UP button released S6_11 retlw .0 ; shouldn't be here, reset state S7_00 retlw .5 ; both buttons pressed again, change state S7_01 retlw .7 ; no change S7_10 retlw .0 ; shouldn't be here, reset state S7_11 retlw .13 ; UP button released, change state S8_00 retlw .6 ; both buttons pressed again, change state S8_01 retlw .0 ; shouldn't be here, reset state S8_10 retlw .8 ; no change S8_11 retlw .14 ; DOWN button released, change state S9_00 retlw .5 ; both buttons pressed again, change state S9_01 retlw .0 ; shouldn't be here, reset state S9_10 retlw .9 ; no change S9_11 retlw .11 ; DOWN button released, change state S10_00 retlw .6 ; both buttons pressed again, change state S10_01 retlw .10 ; no change S10_10 retlw .0 ; shouldn't be here, reset state S10_11 retlw .12 ; DOWN button released, change state S11_00 retlw .0 ; shouldn't be here, reset state S11_01 retlw .0 ; shouldn't be here, reset state S11_10 retlw .0 ; shouldn't be here, reset state S11_11 retlw .0 ; shouldn't be here, reset state S12_00 retlw .0 ; shouldn't be here, reset state S12_01 retlw .0 ; shouldn't be here, reset state S12_10 retlw .0 ; shouldn't be here, reset state S12_11 retlw .0 ; shouldn't be here, reset state S13_00 retlw .0 ; shouldn't be here, reset state S13_01 retlw .0 ; shouldn't be here, reset state

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE (CONTINUED)
S13_10 retlw .0 ; shouldn't be here, reset state S13_11 retlw .0 ; shouldn't be here, reset state S14_00 retlw .0 ; shouldn't be here, reset state S14_01 retlw .0 ; shouldn't be here, reset state S14_10 retlw .0 ; shouldn't be here, reset state S14_11 retlw .0 ; shouldn't be here, reset state S15_00 retlw .0 ; shouldn't be here, reset state S15_01 retlw .0 ; shouldn't be here, reset state S15_10 retlw .0 ; shouldn't be here, reset state S15_11 retlw .0 ; shouldn't be here, reset state

PerformState movf State,w andlw b'00001111' ; mask all states >15 addwf PCL,f ; jump to desired State retlw .0 ; State 0, no action goto State1 ; (2s for repeating LV increment) goto State2 ; (2s for repeating LV decrement) goto State3 goto State4 goto State5 ; (2s for repeating HV increment) goto State6 ; (2s for repeating HV decrement) retlw .7 ; State 7, no action retlw .8 ; State 8, no action retlw .9 ; State 9, no action retlw .10 ; State 10, no action goto State11 goto State12 goto State13 goto State14 goto StateMachineReset ; State 15... shouldn't be here

;* InitGPIO movlw b'00001011' ; initialize UP and DOWN switches to be high & CP to be low. movwf GPIO movlw b'11111100' ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands tris GPIO retlw b'11000000' GPIO_TestUP movlw b'00001011' ; initialize UP and DOWN switches to be high & CP to be low. movwf GPIO movlw b'11111100' ; make both GP0/DECR/CS & GP1/INCR/UD outputs, prevent undesired U/D commands tris GPIO movlw b'11111110' ; make GP1/INCR/UD an input (w/pu enabled) tris GPIO retlw b'10000000' GPIO_TestDOWN movlw b'00001011' ; initialize UP and DOWN switches to be high & CP to be low. movwf GPIO movlw b'11111100' ; make both GP0/DECR/CS & GP1/INCR/UD outputs, prevent undesired U/D commands tris GPIO movlw b'11111101' ; make GP0/DECR/CS an input (w/pu enabled) tris GPIO retlw b'01000000'

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE (CONTINUED)

;**********************************************************************
; Button Isolation Subroutines
;**********************************************************************
; Low Voltage Increment & Decrement Subroutines
;**********************************************************************
LV_Increment
movwf    Exit    ; load the loop counter
bsf    UD
goto    $+1    ; creates a 3us total delay
bcf    CS
movlw    .100    ; 5*100 = 500us delay to pull down CS
movwf    DLYCNT1

DLOOP_LVI
clrwdt    ; or NOP
nop
decfsz    DLYCNT1,f
goto    DLOOP_LVI

LV_IncrLoop
bcf    UD
goto    $+1
bsf    UD
goto    $+1    ; creates a 3us total delay
decfsz    Exit,f    ; Have we incremented the wiper enough?
goto    LV_IncrLoop

IFDEF SaveWiper
bcf    UD
goto    $+1    ; creates a 3us total delay

ENDIF
bsf    CS
retlw    0x00    ; Follow w/long delay to ramp CS & EEPROM Write Cycle

LV_Decrement
movwf    Exit    ; load the loop counter
bcf    UD
goto    $+1    ; creates a 3us total delay
bcf    CS
movlw    .100    ; 5*100 = 500us delay to pull down CS
movwf    DLYCNT1

DLOOP_LVD
clrwdt    ; or NOP
nop
decfsz    DLYCNT1,f
goto    DLOOP_LVD

IFDEF SaveWiper
goto    LV_DecrLoop+4    ; skip first Decrement since final edge is rising

ENDIF

LV_DecrLoop
bsf    UD
goto    $+1    ; creates a 3us total delay
bcf    UD
goto    $+1    ; creates a 3us total delay
decfsz    Exit,f    ; Have we decremented the wiper enough?
goto    LV_DecrLoop

IFDEF SaveWiper
bsf    UD
goto    $+1    ; creates a 3us total delay

ENDIF
bsf    CS    ; Follow w/long delay to ramp CS & EEPROM Write Cycle
retlw    0x01 

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE (CONTINUED)
;* High Voltage Increment & Decrement Subroutines ;** HV_Increment_WL_Disable movwf Exit ; load the loop counter bsf UD goto $+1 ; creates a 3us total delay bsf HV_CS ; starts 1Mhz Charge Pump movlw .100 ; 5100 = 500us delay for Charge Pump ramp time movwf DLYCNT1

DLOOP_HVI clrwdt ;or NOP nop decfsz DLYCNT1,f goto DLOOP_HVI

HV_IncrLoop bcf UD goto $+1 ; creates a 3us total delay bsf UD goto $+1 ; creates a 3us total delay decfsz Exit,f ; Have we incremented the wiper enough? goto HV_IncrLoop bcf HV_CS ; shut off 1Mhz Charge Pump bcf CS ; helps pull the signal down from HV goto $+1 bsf CS retlw 0x02 ; Follow w/long delay to discharge pump & EEPROM Write Cycle

HV_Decrement_WL_Disable movwf Exit ; load the loop counter bcf UD goto $+1 ; creates a 3us total delay bsf HV_CS ; starts 1Mhz Charge Pump movlw .100 ; 5*100 = 500us delay for Charge Pump ramp time movwf DLYCNT1

DLOOP_HVD clrwdt ;or NOP nop decfsz DLYCNT1,f goto DLOOP_HVD

HV_DecrLoop bsf UD goto $+1 ; creates a 3us total delay bcf UD goto $+1 ; creates a 3us total delay decfsz Exit,f ; Have we decremented the wiper enough? goto HV_DecrLoop bcf HV_CS ; shut off 1Mhz Charge Pump bcf CS ; helps pull the signal down from HV goto $+1 bsf CS retlw 0x03 ; Follow w/long delay to discharge pump & EEPROM Write Cycle

HV_Increment_WL_Enable bsf UD goto $+1 ; creates a 3us total delay bsf HV_CS ; starts 1Mhz Charge Pump movlw .100 ; 5*100 = 500us delay for Charge Pump ramp time movwf DLYCNT1

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE (CONTINUED)

DLOOP_HVIWL
    clrwdt ;or NOP
    nop
    decfsz DLYCNT1,f
    goto DLOOP_HVIWL
    bcf UD
    goto $+1 ; creates a 3us total delay
    bsf UD
    goto $+1 ; creates a 3us total delay
    bcf UD
    goto $+1 ; creates a 3us total delay
    bcf HV_CS ; shut off 1Mhz Charge Pump
    bcf CS ; helps pull the signal down from HV
    goto $+1
    bsf CS
    retlw 0x04 ; Follow w/long delay to discharge pump & EEPROM Write Cycle

HV_Decrement_WL_Enable
    bcf UD
    bsf CS
    goto $+1 ; creates a 3us total delay
    bsf HV_CS ; starts 1Mhz Charge Pump
    movlw .100 ; 5*100 = 500us delay for Charge Pump ramp time
    movwf DLYCNT1

DLOOP_HVDWL
    clrwdt ;or NOP
    nop
    decfsz DLYCNT1,f
    goto DLOOP_HVDWL
    bsf UD
    goto $+1 ; creates a 3us total delay
    bcf HV_CS ; shut off 1Mhz Charge Pump
    bcf CS ; helps pull the signal down from HV
    goto $+1
    bsf CS
    retlw 0x05 ; Follow w/long delay to discharge pump & EEPROM Write Cycle

;**************************
; VARIABLE DELAY SUBROUTINES
;**************************
; DLYCNT1 = F9h = 249d DLYCNT2 = W
; DELAY = T((4 DLYCNT1 + 4) DLYCNT2 + 4)
;
; ex. To create a 300ms delay when using a 4Mhz osc, 300-250 = 50
; movlw .50 ;load .50 into WREG
; call VAR1000TcyDELAY ;call VAR1000TcyDELAY = 50ms delay w/4MHz Osc
; call VAR1000TcyDELAY ;call VAR1000TcyDELAY = 250ms delay w/4MHz Osc
; ;total = 300ms delay
;**************************
; The value in W at the time of the CALL = x. Delay = 1000Tcy*x
VAR1000TcyDELAY
movwf DLYCNT2 ; LOADS CONTROLLING DLY # INTO PRIMARY COUNTER
DLOOP2
movlw .249 ; MAXIMIZES THE SECONDARY DLY COUNTER
movwf DLYCNT1

DLOOP1
clrwdt ;or NOP
decfsz DLYCNT1,f ; DECREMENT AND TEST SECONDARY LOOP FOR ZERO
goto DLOOP1 ; CONTINUE SECONDARY LOOP
decfsz DLYCNT2,f ; DECREMENT AND TEST PRIMARY DLY COUNTER
goto DLOOP2 ; CONTINUE PRIMARY LOOP
retlw .250 ; preload W for the next CALL VAR1000TcyDELAY 

TABLE E-1: 00066 MCP402XEV.ASM SOURCE CODE (CONTINUED)

;************************
; VARIABLE 5 Tcy DELAY UP TO 256*5Tcy+5Tcy
; DLYCNT1 = W
; DELAY = T(1 + 5 DLYCNT1 - 1) + CALL + RETLW
;
; ex. To create a 250us delay, (250/5)-1 = 49
; movlw .49 ;load .49 into WREG
; call VAR5TcyDELAY ;call VAR5TcyDELAY
;************************
; The value in W at the time of the CALL = x. Delay = 5*Tcy + 5Tcy
VAR5TcyDELAY
movwf DLYCNT1 ; LOADS CONTROLLING DLY # INTO PRIMARY COUNTER
DLOOP3 clrwdt ;or NOP
nop
decfsz DLYCNT1,f ; DECREMENT AND TEST ZERO
goto DLOOP3 ; CONTINUE LOOP
retlw .250 ; preload W for the next CALL VAR5TcyDELAY
;*************************
end 

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