Mitsubishi Motors DS5000TK User Manual
Page 42
USER’S GUIDE
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PROGRAM STATUS WORD REGISTER
Label:PSW
Register Address: 0D0H
D7
D6
D5
D4
D3
D2
D1
D0
C
AC
F0
RS1
RS0
OV
P
All of the bits in PSW except parity are read/write and are cleared to 0 on any type of reset. The Parity bit is read only
and is cleared to 0 on any type of reset.
Bit Description:
PSW.7:
C
“Carry”:
Set when the previous operation resulted in a carry (during addition) or a
borrow (during subtraction). Otherwise cleared.
PSW.6:
AC
“Auxiliary-Carry”:
Set when the previous operation resulted in a carry (during addition) or a
borrow (during subtraction) from the low–order nibble. Otherwise cleared.
PSW.5:
F0
“User Flag 0”:
General–purpose flag bit which can be set or cleared as needed.
PSW.4–3:
R1–R0
“Register Bank Select”:
Used to select an 8–byte bank of registers within the Data Register space to
be assigned as R0–R8 in subsequent instructions. The 8–byte bank starting
address selection is as follows:
R1
R0
Data Register Address (R0)
0
0
00H
0
1
08H
1
0
10H
1
1
18H
PSW.2: OV
“Overflow”:
Set when a carry was generated into the high–order bit but not a carry out of
the high–order bit as a result of the previous operation, and visa–versa. OV
is normally used in 2’s complement arithmetic.
PSW.0: P
“Parity”:
Set if the modulo–2 sum of the eight bits of the accumulator is 1 (odd parity);
cleared on even parity.