PIC17C752-08/CL MICROCHIP [Microchip Technology], PIC17C752-08/CL Datasheet - Page 52

• Manufacturer Part Number: PIC17C752-08/CL
• Description: High-Performance 8-Bit CMOS EPROM Microcontrollers with 10-bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

PIC17C7XX
7.3
PIC17C7XX devices have a 16 x 16-bit hardware stack
(Figure
or data memory space, and the stack pointer is neither
readable nor writable. The PC (Program Counter) is
“PUSHed” onto the stack when a CALL or LCALL
instruction is executed or an interrupt is acknowledged.
The stack is “POPed” in the event of a RETURN, RETLW,
or a RETFIE instruction execution. PCLATH is not
affected by a “PUSH” or a “POP” operation.
The stack operates as a circular buffer, with the stack
pointer initialized to '0' after all resets. There is a stack
available bit (STKAV) to allow software to ensure that
the stack will not overflow. The STKAV bit is set after a
device reset. When the stack pointer equals Fh, STKAV
is cleared. When the stack pointer rolls over from Fh to
0h, the STKAV bit will be held clear until a device reset.
DS30289A-page 52
7-1). The stack is not part of either the program
Stack Operation
After the device is “PUSHed” sixteen times (without a
“POP”), the seventeenth push overwrites the value
from the first push. The eighteenth push overwrites the
second push (and so on).
Note 1: There is not a status bit for stack under-
Note 2: There are no instruction mnemonics
Note 3: After a reset, if a “POP” operation occurs
flow. The STKAV bit can be used to detect
the underflow which results in the stack
pointer being at the top of stack.
called PUSH or POP. These are actions
that occur from the execution of the CALL,
RETURN, RETLW, and RETFIE instruc-
tions, or the vectoring to an interrupt vec-
tor.
before a “PUSH” operation, the STKAV bit
will be cleared. This will appear as if the
stack is full (underflow has occurred). If a
“PUSH” operation occurs next (before
another “POP”), the STKAV bit will be
locked clear. Only a device reset will
cause this bit to set.
1998 Microchip Technology Inc.