PIC16LC717T-I/SO View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC16LC717T-I/SO

18/20-Pin, 8-Bit CMOS Microcontrollers with 10/12-Bit A/D

Microchip Technology 

PIC16C717/770/771

2.3 PCL and PCLATH

The program counter (PC) specifies the address of the

instruction to fetch for execution. The PC is 13 bits

wide. The low byte is called the PCL register. This reg-

ister is readable and writable. The high byte is called

the PCH register. This register contains the PC<12:8>

bits and is not directly readable or writable. All updates

to the PCH register occur through the PCLATH register.

2.3.1 PROGRAM MEMORY PAGING

PIC16C717/770/771 devices are capable of address-

ing 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 instruc-

tion, the user must ensure that the page select bits are

programmed so that the desired program memory

page is addressed. A return instruction pops a PC

address off the stack onto the PC register. Therefore,

manipulation of the PCLATH<4:3> bits are not required

for the return instructions (which POPs the address

from the stack).

2.4 Stack

The stack allows a combination of up to 8 program calls

and interrupts to occur. The stack contains the return

address from this branch in program execution.

Mid-range devices have 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.

PCLATH is not modified when the stack is PUSHed or

POPed.

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).

DS41120A-page 24

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© 1999 Microchip Technology Inc.

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