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MSM80C154S/83C154S

Program status word register (PSW)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NAME

ADDRESS

MSB

 

 

 

 

 

 

 

 

 

 

LSB

 

7

 

6

5

4

 

3

 

2

 

1

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PSW

0D0H

CY

 

AC

F0

RS1

 

RS0

 

OV

 

F1

P

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIT LOCATION

FLAG

 

 

 

 

FUNCTION

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PSW.0

P

Accumulator (ACC) parity indicator.

 

 

 

 

 

 

 

 

 

 

This bit is "1" when the "1" bit number in the accumulator is an odd number, and

 

 

 

"0" when an even number.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PSW.1

F1

User flag which may be set to "0" or "1" as desired by the user.

 

 

 

 

 

 

 

 

PSW.2

OV

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 executing multiplication instruction (MUL AB) is greater than 0FFH, but is reset

 

 

 

to "0" if the product is less than or equal to 0FFH.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PSW.3

RS0

RAM register bank switch

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RS1

 

RS0

BANK

 

 

 

RAM ADDRESS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

0

0

00H - 07H

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PSW.4

RS1

0

 

1

1

08H - 0FH

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

0

2

10H - 17H

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

1

3

18H - 1FH

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PSW.5

F0

User flag which may be set to "0" or "1" as desired by the user.

 

 

 

 

PSW.6

AC

Auxiliary carry flag.

 

 

 

 

 

 

 

 

 

 

 

 

 

This flag is set to "1" if a carry C3 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".

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PSW.7

CY

Main carry flag.

 

 

 

 

 

 

 

 

 

 

 

 

 

This flag is set to "1" if a carry C7 is generated from bit 7 of the ALU as result of

 

 

 

executing an arithmetic operation instruction.

 

 

 

 

 

 

 

 

 

If a carry C7 is not generated, the flag is reset to "0".

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Image 17
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