chapter seven pic16f87x

Prepared by Eng. Musa AlyamanPrepared by Eng. Musa Alyaman 11

Chapter SevenChapter Seven

PIC16F87x


PIC16F87XA


Devices Included in this Data Sheet

PIC16F873A PIC16F874A PIC16F876A PIC16F877A


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


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)


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


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


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


PIC16F87XA DEVICE FEATURES


The Core 16F873/16F876The Core 16F873/16F876


The Core 16F874/16F877The Core 16F874/16F877


Program MemoryProgram Memory


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).



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).


Data MemoryData Memory


DIRECT/INDIRECT ADDRESSING


CONFIGURATION WORD (ADDRESS 2007h)


Status RegisterStatus Register


INTERRUPT LOGIC


INTCON RegisterINTCON Register


PIE1 RegisterPIE1 Register


PIR1 RegisterPIR1 Register


PIE2 RegisterPIE2 Register


PIR2 RegisterPIR2 Register


ReferencesReferences

1. An Introduction to the Design of Small-Scale Embedded Systems, 1st Ed. By: Tim Wilmshurst Palgrave, 2001

2. The PIC Microcontroller Book 3. Computer Organization & Design by Patterson &

Hennessy.4. Intel Website. www.intel.com5. MicroChip web site www.microchip.com 6. The PIClist internet site.

http://www.intel.com/

http://www.microchip.com/

chapter seven pic16f87x

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