Condition Codes - Samsung S3C8275X User Manual

INSTRUCTION SET

CONDITION CODES

The opcode of a conditional jump always contains a 4-bit field called the condition code (cc). This specifies under
which conditions it is to execute the jump. For example, a conditional jump with the condition code for "equal"
after a compare operation only jumps if the two operands are equal. Condition codes are listed in Table 6-6.
The carry (C), zero (Z), sign (S), and overflow (V) flags are used to control the operation of conditional jump
instructions.
Binary
0000
1000
(note)
0111
(note)
1111
(note)
0110
(note)
1110
1101
0101
0100
1100
(note)
0110
(note)
1110
1001
0001
1010
0010
(note)
1111
(note)
0111
1011
0011
NOTES:
1. It indicates condition codes that are related to two different mnemonics but which test the same flag. For
example, Z and EQ are both true if the zero flag (Z) is set, but after an ADD instruction, Z would probably be used;
after a CP instruction, however, EQ would probably be used.
2. For operations involving unsigned numbers, the special condition codes UGE, ULT, UGT, and ULE must be used.
6-12
Table 6-6. Condition Codes
Mnemonic
F Always false
T Always true
C Carry
NC No carry
Z Zero
NZ Not zero
PL Plus
MI Minus
OV Overflow
NOV No overflow
EQ Equal
NE Not equal
GE Greater than or equal
LT Less than
GT Greater than
LE Less than or equal
UGE Unsigned greater than or equal
ULT Unsigned less than
UGT Unsigned greater than
ULE Unsigned less than or equal
S3C8275X/F8275X/C8278X/F8278X/C8274X/F8274X
Description Flags Set
−
−
C = 1
C = 0
Z = 1
Z = 0
S = 0
S = 1
V = 1
V = 0
Z = 1
Z = 0
(S XOR V) = 0
(S XOR V) = 1
(Z OR (S XOR V)) = 0
(Z OR (S XOR V)) = 1
C = 0
C = 1
(C = 0 AND Z = 0) = 1
(C OR Z) = 1