Siemens SAB 80515 Series User Manual page 25

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 0E0 H
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 0D0 H
0D7 H
0D0 H CY
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 00 H - 07 H
0 1 Bank 1 selected, data address 08 H - 0F H
1 0 Bank 2 selected, data address 10 H - 17 H
1 1 Bank 3 selected, data address 18 H - 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 0F0 H
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 081 H
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 07 H after a reset. This causes the stack to begin at
location 08 H above register bank zero. The SP can be read or written under software control.
Semiconductor Group
0D6 H 0D5 H 0D4 H
AC F0 RS1
0D3 H 0D2 H 0D1 H
RS0 OV
*
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Memory Organization
0D0 H
F1 P PSW