Datasheet

SAM3X / SAM3A [DATASHEET]
Atmel-11057C-ATARM-SAM3X-SAM3A-Datasheet_23-Mar-15
92
10.11.7.2 Condition code suffixes
The instructions that can be conditional have an optional condition code, shown in syntax descriptions as {cond}.
Conditional execution requires a preceding IT instruction. An instruction with a condition code is only executed if
the condition code flags in the APSR meet the specified condition. Table 10-16 shows the condition codes to use.
You can use conditional execution with the IT instruction to reduce the number of branch instructions in code.
Table 10-16 also shows the relationship between condition code suffixes and the N, Z, C, and V flags.
10.11.7.3 Absolute value
The example below shows the use of a conditional instruction to find the absolute value of a number. R0 = ABS(R1).
MOVS R0, R1 ; R0 = R1, setting flags
IT MI ; IT instruction for the negative condition
RSBMI R0, R1, #0 ; If negative, R0 = -R1
10.11.7.4 Compare and update value
The example below shows the use of conditional instructions to update the value of R4 if the signed values R0 is greater
than R1 and R2 is greater than R3.
CMP R0, R1 ; Compare R0 and R1, setting flags
ITT GT ; IT instruction for the two GT conditions
CMPGT R2, R3 ; If 'greater than', compare R2 and R3, setting flags
MOVGT R4, R5 ; If still 'greater than', do R4 = R5
10.11.8 Instruction width selection
There are many instructions that can generate either a 16-bit encoding or a 32-bit encoding depending on the
operands and destination register specified. For some of these instructions, you can force a specific instruction
size by using an instruction width suffix. The .W suffix forces a 32-bit instruction encoding. The .N suffix forces a
16-bit instruction encoding.
Table 10-16. Condition code suffixes
Suffix Flags Meaning
EQ Z = 1 Equal
NE Z = 0 Not equal
CS or
HS
C = 1 Higher or same, unsigned ≥
CC or
LO
C = 0 Lower, unsigned <
MI N = 1 Negative
PL N = 0 Positive or zero
VS V = 1 Overflow
VC V = 0 No overflow
HI C = 1 and Z = 0 Higher, unsigned >
LS C = 0 or Z = 1 Lower or same, unsigned ≤
GE N = V Greater than or equal, signed ≥
LT N != V Less than, signed <
GT Z = 0 and N = V Greater than, signed >
LE Z = 1 and N != V Less than or equal, signed ≤
AL
Can have any
value
Always. This is the default when no suffix is
specified.