PIC16LC72A-10E/SS 查看數據表（PDF） - Microchip Technology

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PIC16LC72A-10E/SS

28-Pin 8-Bit CMOS Microcontrollers

Microchip Technology 

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 and is

readable and writable. The high byte is called the PCH

register. This register contains the PC<12:8> bits and

is not directly accessible. All updates to the PCH regis-

ter go through the PCLATH register.

2.3.1 STACK

The stack allows any 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 hardware

stack. The stack space is not part of either program or

data space and the stack pointer is not accessible. 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 RET-

FIE 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).

PIC16C62B/72A

2.4 Program Memory Paging

The CALL and GOTO instructions provide 11 bits of

address to allow branching within any 2K program

memory page. When doing a CALL or GOTO instruction,

the upper bit of the address is provided by

PCLATH<3>. The user must ensure that the page

select bit is programmed to address the proper pro-

gram memory page. If a return from a CALL instruction

(or interrupt) is executed, the entire 13-bit PC is popped

from the stack. Therefore, manipulation of the

PCLATH<3> bit is not required for the return instruc-

tions.

© 1999 Microchip Technology Inc.

Preliminary

DS35008B-page 17

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