C8051F2XX Datasheet, PDF (67/146 Pages) Silicon Laboratories – Mixed Signal 8 kB ISP Flash MCU Family

C8051F2xx
9.2.5. Stack
A programmer's stack can be located anywhere in the 256-byte data memory. The stack area is desig-
nated using the Stack Pointer (SP, 0x81) SFR. The SP will point to the last location used. The next value
pushed on the stack is placed at SP+1 and then SP is incremented. A reset initializes the stack pointer to
location 0x07. Therefore, the first value pushed on the stack is placed at location 0x08, which is also the
first register (R0) of register bank 1. Thus, if more than one register bank is to be used, the SP should be
initialized to a location in the data memory not being used for data storage. The stack depth can extend up
to 256 bytes.
The MCU also has built-in hardware for a stack record. The stack record is a 32-bit shift register, where
each Push or increment SP pushes one record bit onto the register, and each Call pushes two record bits
onto the register. (A Pop or decrement SP pops one record bit, and a Return pops two record bits, also.)
The stack record circuitry can also detect an overflow or underflow on the 32-bit shift register, and can
notify the emulator software even with the MCU running full-speed debug.
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