
S3C3410X RISC MICROPROCESSOR
ARM INSTRUCTION SET
3-11
CPSR FLAGS
The data processing operations may be classified as logical or arithmetic. The logical operations (AND, EOR,
TST, TEQ, ORR, MOV, BIC, MVN) perform the logical action on all corresponding bits of the operand or
operands to produce the result. If the S bit is set (and Rd is not R15, see below) the V flag in the CPSR will be
unaffected, the C flag will be set to the carry out from the barrel shifter (or preserved when the shift operation is
LSL #0), the Z flag will be set if and only if the result is all zeros, and the N flag will be set to the logical value of
bit 31 of the result.
Table 3-3. ARM Data Processing Instructions
Assembler Mnemonic
OP Code
Action
AND
0000
Operand1 AND operand2
EOR
0001
Operand1 EOR operand2
WUB
0010
Operand1 – operand2
RSB
0011
Operand2 operand1
ADD
0100
Operand1 + operand2
ADC
0101
Operand1 + operand2 + carry
SBC
0110
Operand1 – operand2 + carry – 1
RSC
0111
Operand2 – operand1 + carry – 1
TST
1000
As AND, but result is not written
TEQ
1001
As EOR, but result is not written
CMP
1010
As SUB, but result is not written
CMN
1011
As ADD, but result is not written
ORR
1100
Operand1 OR operand2
MOV
1101
Operand2 (operand1 is ignored)
BIC
1110
Operand1 AND NOT operand2 (Bit clear)
MVN
1111
NOT operand2 (operand1 is ignored)
The arithmetic operations (SUB, RSB, ADD, ADC, SBC, RSC, CMP, CMN) treat each operand as a 32 bit integer
(either unsigned or 2's complement signed, the two are equivalent). If the S bit is set (and Rd is not R15) the V
flag in the CPSR will be set if an overflow occurs into bit 31 of the result; this may be ignored if the operands
were considered unsigned, but warns of a possible error if the operands were 2's complement signed. The C flag
will be set to the carry out of bit 31 of the ALU, the Z flag will be set if and only if the result was zero, and the N
flag will be set to the value of bit 31 of the result (indicating a negative result if the operands are considered to be
2's complement signed).