User`s guide

8051-Compatible Core LZ87010 Advance User’s Guide
3-4 1/15/03
3.2.5 PSW (Program Status Word) Register
The PSW (Program Status Word) register contains processor status information.
3.2.6 SP (Stack Pointer) Register
The SP (Stack Pointer) register is a pointer for the subroutine and interrupt call stack. The
stack can also be accessed by the PUSH and POP instructions. SP is pre-incremented on
a stack push and post-decremented on a stack pop. The stack pointer points to the top of
the stack, which holds the last byte written.
Table 3-8. PSW Register
BIT 7 6 5 4 3 2 1 0
FIELD CY AC F0 RS1 RS0 OV F1 P
RESET 000 0 0 000
RW RW RW RW RW RW RW RW RO
ADDR 0xD0
Table 3-9. PSW Register Bits
BIT NAME DESCRIPTION
7 CY ALU Carry Flag
6 AC ALU Auxiliary Carry Flag
5 F0 User-Definable Flag 0
4 RS1 Register Bank Select 1
3 RS0 Register Bank Select 0
2 OV ALU Overflow Flag
1 F1 User-Definable Flag 1
0 P Accumulator Parity Flag (read-only)
Table 3-10. SP Register
BIT 7 6 5 4 3 2 1 0
FIELD SP[7] SP[6] SP[5] SP[4] SP[3] SP[2] SP[1] SP[0]
RESET 000 0 0 111
RW RW RW RW RW RW RW RW RW
ADDR 0x81