C509-L_97 SIEMENS [Siemens Semiconductor Group], C509-L_97 Datasheet - Page 23

• Manufacturer Part Number: C509-L_97
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Special Function Register PSW (Address D0 H )
Bit
CY
AC
F0
RS1
RS0
OV
F1
P
B Register
The B register is used by 8-bit multiply and divide instructions 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 07 H after a reset. This causes the stack to begin
a location = 08 H above register bank zero. The SP can be read or written under software control.
Semiconductor Group
Bit No.
D0 H
MSB
D7 H
CY
Function
Carry Flag
Used by arithmetic instructions.
Auxiliary Carry Flag
Used by instructions which execute BCD operations)
General Purpose Flag
Register Bank select control bits
These bits are used to select one of the four register banks.
Overflow Flag
General Purpose Flag
Used by arithmetic instructions.
Parity Flag
Set/cleared by hardware after each instruction cycle to indicate an odd/even
number of “one” bits in the accumulator, i.e. even parity.
RS1
0
0
1
1
D6 H
AC
D5 H
F0
RS0
0
1
0
1
RS1
D4 H
Function
Bank 0 selected, data address 00 H -07 H
Bank 1 selected, data address 08 H -0F H
Bank 2 selected, data address 10 H -17 H
Bank 3 selected, data address 18 H -1F H
2-4
RS0
D3 H
D2 H
OV
D1 H
F1
Fundamental Structure
LSB
D0 H
P
Reset Value : 00 H
PSW
1997-10-01
C509-L