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INTERNAL SPECIFICATIONS
73
4.4.2.7 Program status word register (PSW)
PSW 0D0H CY AC F0 RS1 RS0 OV F1 P
Name Address
MSB LSB
76543210
Bit location Flag Function
PSW.0
PSW.1
PSW.2
PSW.3
PSW.4
PSW.5
PSW.6
PSW.7
P
F1
OV
RS0
RS1
F0
AC
CY
Accumulator (ACC) parity indicator.
"1" when the "1" bit number in the accumulator is an odd number,
and "0" when an even number.
User flag which may be set to "0" or "1" as desired by the user.
Overflow flag which is set if the carry C6 from bit 6 of the ALU or
CY is "1" as a result of an arithmetic operation. The flag is also set
to "1" if the resultant product of a multiplication instruction (MUL
AB) is greater than 0FFH, but is reset to "0" if the product is less
than or equal to 0FFH.
RAM register bank switch
User flag which ma be set to "0" or "1" as desired by the user.
Auxiliary carry flag.
This flag is set to "1" if a carry C
3 is generated from bit 3 of the
ALU as a result of executing an arithmetic operation instruction. In
all other cases, the flag is reset to "0".
Main carry flag.
This flag is set to "1" if a carry C
7 is generated from bit 7 of the
ALU as a result of executing an arithmetic operation instruction. In
all other cases, the flag is reset to "0".
RS1 RS0 BANK RAM ADDRESS
0 0 0 00H – 07H
0 1 1 08H – 0FH
1 0 2 10H – 17H
1 1 3 18H – 1FH