Chapter Seven PIC16F87x

1. Chapter SevenPIC16F87x Prepared by Eng. Musa Alyaman

2. PIC16F87XA Prepared by Eng. Musa Alyaman

3. Devices Included in this Data Sheet • PIC16F873A • PIC16F874A • PIC16F876A • PIC16F877A Prepared by Eng. Musa Alyaman

4. High Performance RISC CPU • Only 35 single word instructions to learn • All single cycle instructions except for program branches, which are two-cycle • Operating speed: DC - 20 MHz clock input • DC - 200 ns instruction cycle • Up to 8K x 14 words of FLASH Program Memory, • Up to 368 x 8 bytes of Data Memory (RAM), • Up to 256 x 8 bytes of EEPROM Data Memory • Pin out compatible to other 28-pin or 40/44-pin PIC16CXXX and PIC16FXXX microcontrollers Prepared by Eng. Musa Alyaman

5. Peripheral Features • Timer0: 8-bit timer/counter with 8-bit prescaler • Timer1: 16-bit timer/counter with crystal/clock • Timer2: 8-bit timer/counter with 8-bit period register, prescaler and postscaler • Two Capture, Compare, PWM modules - Capture is 16-bit, max. resolution is 12.5 ns - Compare is 16-bit, max. resolution is 200 ns - PWM max. resolution is 10-bit • Universal Synchronous Asynchronous Receiver • Transmitter (USART/SCI) with 9-bit address detection • Brown-out detection circuitry for • Brown-out Reset (BOR) Prepared by Eng. Musa Alyaman

6. Analog Features • 10-bit, up to 8 channel Analog-to-Digital Converter (A/D) • Brown-out Reset (BOR) • Analog Comparator module with: - Two analog comparators - Programmable on-chip voltage reference • (VREF) module - Comparator outputs are externally accessible Prepared by Eng. Musa Alyaman

7. Special Microcontroller Features • 100,000 erase/write cycle Enhanced FLASH program memory typical • 1,000,000 erase/write cycle Data EEPROM memory typical • Data EEPROM Retention > 40 years • In-Circuit Serial Programming™ (ICSP™) via two pins • Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation • Programmable code protection • Power saving SLEEP mode • Selectable oscillator options • In-Circuit Debug (ICD) via two pins Prepared by Eng. Musa Alyaman

8. CMOS Technology • Low power, high speed FLASH/EEPROM technology • Wide operating voltage range (2.0V to 5.5V) • Commercial and Industrial temperature ranges • Low power consumption Prepared by Eng. Musa Alyaman

9. PIC16F87XA DEVICE FEATURES Prepared by Eng. Musa Alyaman

10. The Core 16F873/16F876 Prepared by Eng. Musa Alyaman

11. The Core 16F874/16F877 Prepared by Eng. Musa Alyaman

12. Program Memory Prepared by Eng. Musa Alyaman

13. Program Memory Paging PCL and PCLATH • The program counter (PC) is 13 bits wide. The low byte comes from the PCL register, which is a readable and writable register. • The upper bits (PC<12:8>) are not readable, but are indirectly writable through the PCLATH register. • On any RESET, the upper bits of the PC will be cleared. • The following Figure shows the two situations for the loading of the PC. • The upper example in the figure shows how the PC is loaded on a write to PCL (PCLATH<4:0> → PCH). • The lower example in the figure shows how the PC is loaded during a CALL or GOTO instruction (PCLATH<4:3> → PCH). Prepared by Eng. Musa Alyaman

14. Program Memory Paging Prepared by Eng. Musa Alyaman

15. Program Memory Paging COMPUTED GOTO • A computed GOTO is accomplished by adding an offset to the program counter (ADDWF PCL). When doing a table read using a computed GOTO method, care should be exercised if the table location crosses a PCL memory boundary (each 256 byte block). STACK • The PIC16F87XA family has an 8-level deep x 13-bit wide hardware stack. • The stack space is not part of either program or data space and the stack pointer is not readable or writable. • The PC is PUSHed onto the stack when a CALL instruction is executed, or an interrupt causes a branch. • The stack is POPed in the event of a RETURN, RETLW or a RETFIE instruction execution. • The stack operates as a circular buffer. This means that after the stack has been PUSHed eight times, the ninth push overwrites the value that was stored from the first push. The tenth push overwrites the second push (and so on). Call & Goto • All PIC16F87XA devices are capable of addressing a continuous 8K word block of program memory. • The CALL and GOTO instructions provide only 11 bits of address to allow branching within any 2K program memory page. • When doing a CALL or GOTO instruction, the upper 2 bits of the address are provided by PCLATH<4:3>. • When doing a CALL or GOTO instruction, the user must ensure that the page select bits are programmed so that the desired program memory page is addressed. • If a return from a CALL instruction (or interrupt) is executed, the entire 13-bit PC is popped off the stack. Therefore, manipulation of the PCLATH<4:3> bits is not required for the return instructions (which POPs the address from the stack). Prepared by Eng. Musa Alyaman

16. Program Memory Paging Prepared by Eng. Musa Alyaman

17. Program Memory Paging Prepared by Eng. Musa Alyaman

18. Program Memory Paging Prepared by Eng. Musa Alyaman

19. Data Memory Prepared by Eng. Musa Alyaman

20. DIRECT/INDIRECT ADDRESSING Prepared by Eng. Musa Alyaman

21. CONFIGURATION WORD (ADDRESS 2007h) Prepared by Eng. Musa Alyaman

22. Status Register Prepared by Eng. Musa Alyaman

23. INTERRUPT LOGIC Prepared by Eng. Musa Alyaman

24. INTCON Register Prepared by Eng. Musa Alyaman

25. PIE1 Register Prepared by Eng. Musa Alyaman

26. PIR1 Register Prepared by Eng. Musa Alyaman

27. PIE2 Register Prepared by Eng. Musa Alyaman

28. PIR2 Register Prepared by Eng. Musa Alyaman

29. References • An Introduction to the Design of Small-Scale Embedded Systems, 1st Ed. By: Tim Wilmshurst Palgrave, 2001 • The PIC Microcontroller Book • Computer Organization & Design by Patterson & Hennessy. • Intel Website. www.intel.com • MicroChip web site www.microchip.com • The PIClist internet site. Prepared by Eng. Musa Alyaman