C511_1 Datasheet, PDF (18/128 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

Fundamental Structure
Special Function Register PSW (Address D0H)
MSB
Bit No. 7
6
D0H CY AC
5
4
3
2
F0 RS1 RS0 OV
Reset Value : 00H
LSB
1
0
F1
P
PSW
Bit
CY
AC
F0
RS1 RS0
00
01
10
11
OV
F1
P
Function
Carry Flag
Auxiliary Carry Flag (for BCD operations)
General Purpose Flag
Register Bank select control bits
Bank 0 selected, data address 00H-07H
Bank 1 selected, data address 08H-0FH
Bank 2 selected, data address 10H-17H
Bank 3 selected, data address 18H-1FH
Overflow Flag
General Purpose Flag
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
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
The stack pointer (SP) register is 8 bits wide. It is incremented 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
the on-chip RAM, the stack pointer is initialized to 07H after a reset. This causes the stack to begin
a location = 08H above register bank zero. The SP can be read or written under software control.
Semiconductor Group
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