The Quintessential Pic Microcontroller

Sid Katzen

The Quintessential PIC

Microcontroller

SPIN Springer’s internal project number, if known

Engineering – Monograph (English)

November 8, 2000

Springer-Verlag

Berlin Heidelberg NewYork

London Paris Tokyo

Hong Kong Barcelona

Budapest

Contents

List of Figures . ................................................ VI

List of Tables . ................................................. XI

List of Programs . .............................................. XIV

Part I The Fundamentals

1. Digital Representation . .................................... 3

2. Logic Circuitry . ............................................ 17

3. Stored Program Processing . ................................ 41

Part II The Software

4. The PIC16F84 Microcontroller . .............................. 77

5. The Instruction Set . ........................................ 105

6. Subroutines and Modules . .................................. 137

7. Interrupt Handling . ........................................ 171

8. Assembly language ......................................... 197

9. High-Level Language . ...................................... 231

Part III The Outside World

10. The Real World . ........................................... 253

11. One Byte at a Time . ........................................ 271

VI Contents

12. One Bit at a Time . ......................................... 305

13. Time is of the Essence . ..................................... 361

14. Take the Rough with the Smooth . ........................... 391

15. To Have and to Hold . ...................................... 431

16. A Case Study . ............................................. 455

Appendices

A. 14-bit Core Instruction Set . ................................. 475

B. Special Purpose Register Structure for the PIC16C74B . ........ 477

C. C Instruction Set . .......................................... 479

D. Acronyms and Abbreviations . .............................. 481

Index . ........................................................ 485

List of Figures

1.1 The NOT operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.2 The AND function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.3 The inclusive-OR operation.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.4 The XOR operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

1.5 Detecting sign overflow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.1 The 74LS00 quad 2-I/P NAND package. . . . . . . . . . . . . . . . . . . . . . . 18

2.2 Output structures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.3 Open-collector buffers driving a party line. . . . . . . . . . . . . . . . . . . 20

2.4 Sharing a bus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2.5 The 74LS138 and ’139 MSI natural decoders. . . . . . . . . . . . . . . . . 21

2.6 The 74LS688 octal equality detector. . . . . . . . . . . . . . . . . . . . . . . . . 23

2.7 Addition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.8 Implementing a programmable adder/subtractor. . . . . . . . . . . . 25

2.9 The 74LS382 ALU. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

2.10 A ROM-implemented 1-bit adder. . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

2.11 The 2764 Erasable PROM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

2.12 Floating-gate MOSFET link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

2.13 The R S latch.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

2.14 Using a RS latch to debounce a switch. . . . . . . . . . . . . . . . . . . . . . . 30

2.15 The D latch and flip flop. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

2.16 The 74LS74 dual D flip flop. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

2.17 The 74LS377 octal D flip flop array. . . . . . . . . . . . . . . . . . . . . . . . . . 33

2.18 The 74LS373 octal D latch array. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

2.19 An 8-bit ALU-accumulator processor. . . . . . . . . . . . . . . . . . . . . . . . 35

2.20 The SISO shift register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

2.21 The T flip flop. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

2.22 A modulo-16 ripple counter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

2.23 Generating timing waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

2.24 The 6264 8196 × 8 RAM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.1 An elementary von Neumann computer. . . . . . . . . . . . . . . . . . . . . . 42

3.2 An elementary Harvard architecture computer. . . . . . . . . . . . . . . 44

3.3 Executing the 1st instruction whilst fetching down the 2nd. . . 45

3.4 Parallel fetch and execute streams. . . . . . . . . . . . . . . . . . . . . . . . . . . 50

VIII List of Figures

3.5 Programmer’s model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

3.6 The indirect mechanism. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

3.7 Circular shifts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

3.8 The process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

3.9 Visualization of the taskprocess. . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

3.10 Division by repetitive subtracting. . . . . . . . . . . . . . . . . . . . . . . . . . . 68

3.11 Double-precision shifting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

3.12 A 7-bit pseudo-random number generator. . . . . . . . . . . . . . . . . . . 70

4.1 An example of a system based on a microcontroller. . . . . . . . . . 81

4.2 Architecture of the PIC16F84 microcontroller . . . . . . . . . . . . . . . 85

4.3 Showing how all of the PC are altered when writing to PCL.. . . 86

4.4 Internal clocksequencing waveforms. . . . . . . . . . . . . . . . . . . . . . . . 87

4.5 The PIC16F84 Status register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

4.6 Data store memory map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

5.1 General 14-bit core Status register. . . . . . . . . . . . . . . . . . . . . . . . . . . 109

5.2 The indirect mechanism. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

5.3 The ith section of the compare-update sequence. . . . . . . . . . . . . 112

5.4 Generating a 13-bit Program-store address. . . . . . . . . . . . . . . . . . . 114

6.1 Modular hardware implementing a PC. . . . . . . . . . . . . . . . . . . . . . . 138

6.2 Subroutine calling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

6.3 Using the hardware stackhold return addresses. . . . . . . . . . . . . 141

6.4 Nested subroutines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

6.5 System view of K × 100 ms delay subroutine. . . . . . . . . . . . . . . . . 145

6.6 The 7-segment display. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

6.7 System diagram for the byte multiplication subroutine. . . . . . . 150

6.8 The stackframe. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

6.9 Finding the square root of an integer. . . . . . . . . . . . . . . . . . . . . . . . 162

7.1 Detecting and measuring an external event. . . . . . . . . . . . . . . . . . 172

7.2 Responding to an interrupt request.. . . . . . . . . . . . . . . . . . . . . . . . . 175

7.3 The flag:maskpair. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176

7.4 The PIC 16F84’s interrupt logic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

7.5 Oven safety hardware. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

7.6 Echo sounding hardware. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

8.1 Conversion from assembly-level source to machine code. . . . . 198

8.2 Absolute assembly-level code translation. . . . . . . . . . . . . . . . . . . . 202

8.3 Relocatable assembly-level code translation. . . . . . . . . . . . . . . . . . 211

8.4 Linking three source files. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

8.5 Code building and testing tools. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

8.6 MPLAB window. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

8.7 MPLAB screen shot. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

List of Figures IX

9.1 Conversion from high-level source code to machine code. . . . . 233

9.2 Onion skin view of the steps leading to executable code. . . . . . 234

9.3 Simulating our example program in MPLAB. . . . . . . . . . . . . . . . . . 242

9.4 The active-low die patterns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

10.1 Pinout for a variety of PIC family members. . . . . . . . . . . . . . . . . . 254

10.2 Typical supply current versus clocking frequency. . . . . . . . . . . . 256

10.3 Equivalent output circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

10.4 Typical oscillator configurations.. . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

10.5 Configuration word for the PIC16F83/4. . . . . . . . . . . . . . . . . . . . . . 261

10.6 Manually resetting the PIC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

10.7 The sequence of events leading to startup on power-up. . . . . . 264

10.8 Brown-out reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

10.9 An alternative brown-out circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

11.1 The mid-range PIC 16CXX series Parallel Ports A and B. . . . . . . 272

11.2 A simplified typical I/O port line. . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

11.3 Reading and writing to a port bit set to input or output. . . . . . 275

11.4 Sinking and sourcing current. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276

11.5 Port A I/O pin driver structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278

11.6 Interfacing switches to a port line. . . . . . . . . . . . . . . . . . . . . . . . . . . 280

11.7 Port B’s weakpull-up option. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280

11.8 Interfacing to a keypad. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

11.9 The Port B change feature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

11.10 A multi-zone intruder alarm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

11.11 Source current against voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290

11.12 The stepper motor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

11.13 Using port expansion to drive three 7-segment displays. . . . . . 298

11.14 Scanning a 3-digit 7-segment array. . . . . . . . . . . . . . . . . . . . . . . . . . 299

11.15 Low-level output voltage against sinkcurrent. . . . . . . . . . . . . . . . 304

12.1 The smart card. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305

12.2 Serial interface to a 3-digit 7-segment display. . . . . . . . . . . . . . . . 307

12.3 Logic functional diagram of the 74HCT595 octal shift register. 309

12.4 Serially interfacing to a DAC0800 digital to analog converter. 310

12.5 Serially interfacing to the multi-zone intruder alarm. . . . . . . . . 311

12.6 The MAX549A SPI dual 8-bit DAC. . . . . . . . . . . . . . . . . . . . . . . . . . . 314

12.7 SPI waveforms for the MAX549A. . . . . . . . . . . . . . . . . . . . . . . . . . . . 316

12.8 Multiple MAX549As on the one SPI circuit. . . . . . . . . . . . . . . . . . . 316

12.9 The basic Serial Synchronous Port. . . . . . . . . . . . . . . . . . . . . . . . . . . 317

12.10 The SSP CONtrol and STATus registers. . . . . . . . . . . . . . . . . . . . . . 318

12.11 SSP SPI-mode master waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . 321

12.12 A multidrop SPI communications network. . . . . . . . . . . . . . . . . . . 322

12.13 Data transfer on the I

2C bus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325

12.14 Sharing the SCL and SDA bus lines. . . . . . . . . . . . . . . . . . . . . . . . . . . 326

X List of Figures

12.15 A I

2C packet transmission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327

12.16 The MAXIM MAX518 I

2C dual digital to analog converter. . . . . 328

12.17 Minimum timing relationships for the Fast I

2C mode. . . . . . . . . 329

12.18 Transmitting the string "PIC" in the asynchronous mode . . . . . 336

12.19 The PIC USART configured for asynchronous communication. 342

12.20 Some signalling configurations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

12.21 Communicating with a PC via an RS-232 link. . . . . . . . . . . . . . . . . 349

12.22 The 24XXX series of I2C serial EEPROMs. . . . . . . . . . . . . . . . . . . . . 352

12.23 EEPROM Read and Write waveforms. . . . . . . . . . . . . . . . . . . . . . . . . 355

12.24 Interfacing the DS1820 1-Wire digital thermometer. . . . . . . . . . 356

12.25 A LCD display. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360

13.1 The integral PIC Watchdog timer. . . . . . . . . . . . . . . . . . . . . . . . . . . . 362

13.2 The Option register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363

13.3 Simplified equivalent circuit for Timer 0. . . . . . . . . . . . . . . . . . . . . 365

13.4 Counting cans of beans on a conveyer belt. . . . . . . . . . . . . . . . . . . 366

13.5 Functional equivalent circuit for Timer 1 . . . . . . . . . . . . . . . . . . . . 372

13.6 The CCP1 module set to Compare mode. . . . . . . . . . . . . . . . . . . . . 375

13.7 Capturing the time of an event. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377

13.8 A simplified equivalent circuit for Timer 2. . . . . . . . . . . . . . . . . . . 379

13.9 Pulse width modulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380

13.10 Timer 2 and the PWM CCP mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381

13.11 An event manifesting itself as a pulse duration. . . . . . . . . . . . . . 387

14.1 Analog world – digital processing. . . . . . . . . . . . . . . . . . . . . . . . . . . 391

14.2 The quantizing process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393

14.3 The analog–digital process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396

14.4 Illustrating aliasing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397

14.5 Initializing the 8-4-2-1 capacitor network. . . . . . . . . . . . . . . . . . . . 398

14.6 Simplified view of the A/D converter. . . . . . . . . . . . . . . . . . . . . . . . 400

14.7 The successive approximation process. . . . . . . . . . . . . . . . . . . . . . 402

14.8 The 8-bit 8-channel analog to digital conversion module. . . . . 404

14.9 Configuring the analog inputs for Port A and Port E.. . . . . . . . . . 405

14.10 Interrupt control for the ADC module. . . . . . . . . . . . . . . . . . . . . . . 408

14.11 R-2R digital-to-analog conversion. . . . . . . . . . . . . . . . . . . . . . . . . . . . 416

14.12 The Maxim MAX506 quad 8-bit D/A converter. . . . . . . . . . . . . . . 418

14.13 Generating a continuous sawtooth using a MAX506 DAC. . . . . 419

14.14 Buffered data acquisition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420

14.15 A level-shifting resistor network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423

14.16 ECG detection strategy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 426

14.17 A controllable external voltage circuit. . . . . . . . . . . . . . . . . . . . . . . 429

14.18 Pinning for the PIC16C71. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429

15.1 The PIC16F8X Data EEPROM module. . . . . . . . . . . . . . . . . . . . . . . . . 433

15.2 The PIC16F8X EECON1 register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434

List of Figures XI

15.3 The first 32 bytes of EEPROM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438

15.4 The PIC16F87X flash and Data EEPROM storage system. . . . . . . 440

15.5 The PIC16F87X EEPROM Control register 1. . . . . . . . . . . . . . . . . . . 441

15.6 View of the flash Program module. . . . . . . . . . . . . . . . . . . . . . . . . . . 445

15.7 Configuration word for the PIC16F87X devices. . . . . . . . . . . . . . . 445

15.8 Watchdog timer period versus temperature. . . . . . . . . . . . . . . . . . 448

16.1 The annunciator hardware. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456

16.2 The modular software structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458

16.3 The Main process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 468

16.4 Programming the PIC from MPLAB. . . . . . . . . . . . . . . . . . . . . . . . . . . 472

16.5 The Microchip PICSTART Plus programmer. . . . . . . . . . . . . . . . . . 473

List of Tables

1.1 7-bit ASCII characters. ...................................... 5

1.2 Some common bit groupings. ............................... 6

1.3 Different ways of representing the quantities decimal 0…20. . 7

3.1 Our BASIC computer’s instruction set. . . . . . . . . . . . . . . . . . . . . . . 53

5.1 Move instructions.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

5.2 Arithmetic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

5.3 Logic instructions.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

5.4 Program Counter instructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

6.1 Subroutine and interrupt handling instructions. . . . . . . . . . . . . . 139

6.2 The 7-segment lookup table showing byte[N] being extracted. 149

8.1 The listing file root.lst. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

8.2 The absolute 8-bit Intel format object-code file root.hex. . . . 206

8.3 The error file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

8.4 Part of Microchip’s file p16f84.inc. . . . . . . . . . . . . . . . . . . . . . . . . 209

8.5 The pic16f84.lkr linker command file. . . . . . . . . . . . . . . . . . . . . 212

8.6 The output linker map file rms.asm. . . . . . . . . . . . . . . . . . . . . . . . . 218

8.7 The resulting absolute object file rms.hex. . . . . . . . . . . . . . . . . . . 219

9.1 Resulting assembly-level CCS compiler output after linking.. . 240

10.1 PIC16F83/4 Special-Purpose Register file reset summary. . . . . 263

10.2 Power-up reset and sleep timeouts. . . . . . . . . . . . . . . . . . . . . . . . . 265

10.3 Reset conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266

11.1 Summary of mid-range PIC parallel I/O provision. . . . . . . . . . . . 272

11.2 Energization pattern for the eight field directions. . . . . . . . . . . . 294

12.1 The SSP Mode bits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319

14.1 Quantization parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394

14.2 ADC clocking frequency versus device crystal frequency. . . . . 401

14.3 Configuring the ADC port pins in the PIC16C73/74 devices. . . 405

List of Programs

3.1 Clearing a blockof files the linear way. . . . . . . . . . . . . . . . . . . . . . . 56

3.2 Clearing a blockof files using a repeating loop. . . . . . . . . . . . . . . 57

3.3 Simple single-precision addition of two byte variables. . . . . . . . 64

3.4 A more accurate single-precision addition. . . . . . . . . . . . . . . . . . . 64

3.5 The double-precision add program. . . . . . . . . . . . . . . . . . . . . . . . . . 66

3.6 Dividing by ten. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

3.7 Multiplying by nine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

3.8 A 7-bit pseudo-random number generator. . . . . . . . . . . . . . . . . . . 71

4.1 Incrementing a packed BCD byte. . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

4.2 Adding two packed BCD numbers. . . . . . . . . . . . . . . . . . . . . . . . . . . 103

5.1 Finding the maximum temperature the linear way. . . . . . . . . . . . 111

5.2 Finding the maximum temperature using a loop structure. . . . 113

5.3 Division by repetitive subtraction. . . . . . . . . . . . . . . . . . . . . . . . . . . 118

5.4 Shifting to find the highest set bit. . . . . . . . . . . . . . . . . . . . . . . . . . . 124

5.5 Triple-precision shifting to find the number of set bits. . . . . . . 125

5.6 Multiplying by three. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

5.7 Double-precision decrement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

5.8 Bi-quinary error detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

5.9 Binary to 2-digit BCD conversion. . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

5.10 Average daily temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

5.11 multiplication by ten. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

6.1 A 100 ms delay subroutine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

6.2 A K × 100 ms delay subroutine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

6.3 An alternative K × 100 ms delay subroutine. . . . . . . . . . . . . . . . . 147

6.4 The software 7-segment decoder. . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

6.5 The byte multiplication subroutine. . . . . . . . . . . . . . . . . . . . . . . . . . 152

6.6 Implementing a byte multiply using a stackmodel. . . . . . . . . . . 157

6.7 Dividing by three . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

6.8 Coding a 208 µs delay. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

6.9 A 1-second delay program. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

6.10 Binary to 3-digit BCD conversion. . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

6.11 Coding the square root subroutine. . . . . . . . . . . . . . . . . . . . . . . . . . 163

6.12 Using a software stackto pass parameters. . . . . . . . . . . . . . . . . . . 166

6.13 The software 7-segment decoder revisited. . . . . . . . . . . . . . . . . . . 166

XVI List of Programs

7.1 Background program for the pea canning packer. . . . . . . . . . . . . 181

7.2 Event counting foreground software. . . . . . . . . . . . . . . . . . . . . . . . . 183

7.3 Oven safety.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

7.4 Saving and restoring the context for the PIC16C74 processor. 191

7.5 Coding the real-time clockISR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

7.6 Incrementing a packed-BCD byte with maximum value of 99.. 194

8.1 Absolute assembly-level code for our square-root module. . . . 200

8.2 The main relocatable source file main.asm. . . . . . . . . . . . . . . . . . . 214

8.3 The relocatable source file sqr.asm. . . . . . . . . . . . . . . . . . . . . . . . . 215

8.4 The relocatable source file root2.asm. . . . . . . . . . . . . . . . . . . . . . . 216

9.1 A simple function coded in C.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

9.2 Coding the square root function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

9.3 Linearizing a K-type thermocouple. . . . . . . . . . . . . . . . . . . . . . . . . . 246

9.4 Generating the root-mean square value of two variables. . . . . . 247

11.1 Scanning the keypad. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283

11.2 Noise filtered keypad scanning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284

11.3 Interacting with the intruder hardware. . . . . . . . . . . . . . . . . . . . . . 288

11.4 A digital comparator with hysteresis. . . . . . . . . . . . . . . . . . . . . . . . 292

11.5 Driving a stepper motor.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293

11.6 Coding the keypad device driver in C. . . . . . . . . . . . . . . . . . . . . . . . 297

11.7 Displaying the decimal equivalent of a binary byte. . . . . . . . . . . 301

11.8 Displaying a 3-digit decimal number on a scanning readout. . 302

12.1 Displaying the decimal equivalent of a binary byte. . . . . . . . . . . 308

12.2 Input serial byte subroutine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312

12.3 Interacting with the MAX549A dual-channel SPI DAC. . . . . . . . . 315

12.4 Using the SSP for SPI data input and output. . . . . . . . . . . . . . . . . . 320

12.5 Interfacing to the MAX549A in C. . . . . . . . . . . . . . . . . . . . . . . . . . . . 323

12.6 A crystal frequency-independent short delay macro. . . . . . . . . . 331

12.7 Low-level I

2C subroutines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332

12.8 Interacting with the MAX518 dual-channel I

2C DAC. . . . . . . . . . 334

12.9 Interfacing to the MAX518 in C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

12.10 A baud-rate delay macro. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338

12.11 Asynchronous formatted input and output subroutines. . . . . . 340

12.12 The USART-based I/O subroutines. . . . . . . . . . . . . . . . . . . . . . . . . . . 345

12.13 Updating Program 11.4’s trip value. . . . . . . . . . . . . . . . . . . . . . . . . . 350

12.14 Reading in a byte using the I

2C protocol. . . . . . . . . . . . . . . . . . . . . 351

12.15 Incrementing the non-volatile odometer count. . . . . . . . . . . . . . . 354

12.16 Reading and writing on a 1-Wire system. . . . . . . . . . . . . . . . . . . . . 358

13.1 The bean counter Interrupt Service Routine. . . . . . . . . . . . . . . . . . 368

13.2 Measuring the ECG waveform period to a resolution of 1 ms. . 370

13.3 Generating a 15 minute data logger timebase. . . . . . . . . . . . . . . . 374

13.4 Capturing the instant of time an ECG R-point occurs. . . . . . . . . 378

13.5 Pulse-Width Modulation using Timer 0. . . . . . . . . . . . . . . . . . . . . . . 384

13.6 Tachometer software. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386

List of Programs XVII

13.7 Measuring the duration of a pulse. . . . . . . . . . . . . . . . . . . . . . . . . . . 388

14.1 Taking a reading from channel n. . . . . . . . . . . . . . . . . . . . . . . . . . . . 407

14.2 Interrupt-driven subroutine to read channel n. . . . . . . . . . . . . . . 410

14.3 The ISR for our interrupt-driven ADC software. . . . . . . . . . . . . . . 411

14.4 Digitizing Channel 1 of a PIC16C71 device. . . . . . . . . . . . . . . . . . . 412

14.5 A digital/analog comparator with hysteresis. . . . . . . . . . . . . . . . . 414

14.6 Buffered interrupt-driven data acquisition. . . . . . . . . . . . . . . . . . . 421

14.7 Sleep conversion in C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422

14.8 ECG peakpicking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425

14.9 An implementation of the ECG peakpicker in C. . . . . . . . . . . . . . 427

15.1 Retrieving a byte from the EEPROM Data module. . . . . . . . . . . . . 434

15.2 Putting a byte into the EEPROM Data module.. . . . . . . . . . . . . . . . 436

15.3 Incrementing the non-volatile odometer count in Data EEPROM. 437

15.4 Reading a word from the flash Program store. . . . . . . . . . . . . . . . 442

15.5 Writing to flash Program memory. . . . . . . . . . . . . . . . . . . . . . . . . . . 443

15.6 Squaring an integer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444

15.7 C-based coding for the odometer. . . . . . . . . . . . . . . . . . . . . . . . . . . . 446

15.8 The Sauna Power-up reset sequence and ISR. . . . . . . . . . . . . . . . . 450

15.9 Reading a new period count. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451

15.10 Updating the Sauna EEPROM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452

16.1 The timebase software. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461

16.2 The data display function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463

16.3 The initialization code. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465

16.4 The Diagnostic process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 466

16.5 The Set-time process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467

16.6 The Main process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 471