SAB80515 Datasheet, PDF (25/270 Pages) Siemens Semiconductor Group – 8-Bit Single-Chip Microcontroller Family

Memory Organization
The following paragraphs give a general overview of the special function register and refer to
sections where a more detailed description can be found.
Accumulator, SFR Address 0E0H
ACC is the symbol for the accumulator register. The mnemonics for accumulator-specific
instructions, however, refer to the accumulator simply as A.
Figure 4-4
Program Status Word Register (PSW), SFR Address 0D0H
0D7H 0D6H 0D5H 0D4H 0D3H 0D2H 0D1H 0D0H
0D0H CY
AC
F0 RS1 RS0 OV
F1
P PSW
The PSW register contains program status information.
Bit
Function
CY
Carry flag
AC
Auxiliary carry flag (for BCD operations)
F0
General purpose user flag 0
RS1 RS0 Register bank select control bits
0
0 Bank 0 selected, data address 00H - 07H
0
1 Bank 1 selected, data address 08H - 0FH
1
0 Bank 2 selected, data address 10H - 17H
1
1 Bank 3 selected, data address 18H - 1F7
OV
Overflow flag
F1
General purpose user flag
P
Parity flag. Set/cleared by hardware each instruction cycle to indicate an odd/
even number of "one" bits in the accumulator, i.e. even parity.
B Register, SPF Address 0F0H
The B register is used during multiply and divide and serves as both source and destination. For
other instructions it can be treated as another scratch pad register.
Stack Pointer, SFR Address 081H
The Stack Pointer (SP) register is 8 bits wide. It is incriminated before data is stored during PUSH
and CALL executions and decremented after data is popped during a POP and RET (RETI)
execution, i.e. it always points to the last valid stack byte. While the stack may reside anywhere in
on-chip RAM, the stack pointer is initialized to 07H after a reset. This causes the stack to begin at
location 08H above register bank zero. The SP can be read or written under software control.
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