Zilog Z80180 Bedienungsanleitung PDF herunterladen (Seite 194)

Z8018x

Family MPU User Manual

UM005003-0703

179

6Z R/W0Zero.

Z is set to 1 when instruction execution produces 0 result.

Otherwise, Z is reset to 0.

5 Not Used ? ? Not used

4H R/W0Half Carry.

H is used by the DAA (Decimal Adjust Accumulator)

instruction to reflect borrow or carry from the least

significant 4 bits and thereby adjust the results of BCD

addition and subtraction.

3 Not Used ? ? Not used.

2P/VR/W0P/V: Parity/Overflow.

P/V serves a dual purpose. For logical operations P/V is

set to 1 if the number of 1 bit in the result is even and P/V

is reset to 0 if the number of 1 in the result is odd. For two

complement arithmetic, P/V is set to 1 if the operation

produces a result which is outside the allowable range

(+ 127 to -128 for 8-bit operations, + 32767 to - 32768 for

16-bit operations).

1N R/W0Negative.

N is set to 1 if the last arithmetic instruction was a subtract

operation (SUB, DEC, CP, etc.) and N is reset to 0 if the

last arithmetic instruction was an addition operation (ADD,

INC, etc.).

0C R/W0Carry.

C is set to 1 when a carry (addition) or borrow (subtraction)

from the most significant bit of the result occurs. C is also

affected by Accumulator logic operations such as shifts

and rotates.

Bit

Position Bit/Field R/W Value Description

1 2 ... 189 190 191 192 193 194 195 196 197 198 199 ... 325 326

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