Z8 Microcontrollers
ZiLOG Instruction Set
UM001601-0803 12-5
12.3 CONDITION CODES
The C, Z, S, and V Flags control the operation of the ‘Condition-
al’ Jump instructions. Sixteen frequently useful functions of the
flag settings are encoded in a 4-bit field called the condition code
(cc), which forms bits 4-7 of the conditional instructions.
Condition codes and flag settings are summarized in Tables 12-
9, 12-10, and 12-11. Notation for the flags and how they are af
-
fected are as follows:
Table 12-9. Z8 Flag Definitions
Flag Description
C Carry Flag
Z Zero Flag
S Sign Flag
V Overflow Flag
D Decimal Adjust Flag
H Half Carry Flag
Table 12-10. Flag Settings Definitions
Symbol Definition
0 Cleared to 0
1 Set to 1
* Set or cleared according to operation
– Unaffected
X Undefined
Table 12-11. Condition Codes
Binary HEX Mnemonic Definition Flag Settings
0000 0 F Always False –
1000 8 (blank) Always True –
0111 7 C Carry C = 1
1111 F NC No Carry C = 0
0110 6 Z Zero Z = 1
1110 E NZ Non-Zero Z = 0
1101 D PL Plus S = 0
0101 5 Ml Minus S = 1
0100 4 OV Overflow V = 1
1100 C NOV No Overflow V = 0
0110 6 EQ Equal Z = 1
1110 E NE Not Equal Z = 0
1001 9 GE Greater Than or Equal (S XOR V) = 0
0001 1 LT Less Than (S XOR V) = 1
1010 A GT Greater Than (Z OR (S XOR V)) = 0
0010 2 LE Less Than or Equal (Z OR (S XOR V)) = 1
1111 F UGE Unsigned Greater Than or Equal C = 0
0111 7 ULT Unsigned Less Than C = 1
1011 B UGT Unsigned Greater Than (C = 0 AND Z = 0) = 1
0011 3 ULE Unsigned Less Than or Equal (C OR Z) = 1
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