Zilog Z80380 User Manual
Page 37
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ANUAL
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ILOG
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5.2.7 Condition Codes
The Carry, Zero, Sign, and Parity/Overflow flags are used
to control the operation of the conditional instructions. The
operation of these instructions is a function of the state of
one of the flags. Special mnemonics called condition
codes are used to specify the flag setting to be tested
during execution of a conditional instruction; the condition
codes are encoded into a 3-bit field in the instruction
opcode itself.
Table 5-1 lists the condition code mnemonic, the flag
setting it represents, and the binary encoding for each
condition code.
Table 5-1. Condition codes
Condition Codes for Jump, Call, and Return Instructions
Mnemonic
Meaning
Flag Setting
Binary Code
NZ
Not Zero*
Z = 0
000
Z
Zero*
Z = 1
001
NC
No Carry*
C = 0
010
C
Carry*
C = 1
011
NV
No Overflow
V = 0
100
PO
Parity Odd
V = 0
100
V
Overflow
V = 1
101
PE
Parity Even
V = 1
101
NS
No Sign
S = 0
110
P
Plus
S = 0
110
S
Sign
S = 1
111
M
Minus
S = 1
111
*Abbreviated set
Condition Codes for Jump Relative and Call Relative Instructions
Mnemonic
Meaning
Flag Setting
Binary Code
NZ
Not Zero
Z = 0
100
Z
Zero
Z = 1
101
NC
No Carry
C = 0
110
C
Carry
C = 1
111