Datasheet

11011B–ATARM–21-Feb-12

SAM3N

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.

If you specify an instruction width suffix and the assembler cannot generate an instruction

encoding of the requested width, it generates an error.

In some cases it might be necessary to specify the .W suffix, for example if the operand is the

label of an instruction or literal data, as in the case of branch instructions. This is because the

assembler might not automatically generate the right size encoding.

10.11.8.1 Instruction width selection

To use an instruction width suffix, place it immediately after the instruction mnemonic and condition code, if any. The exam-

ple below shows instructions with the instruction width suffix.

BCS.W label ; creates a 32-bit instruction even for a short branch

ADDS.W R0, R0, R1 ; creates a 32-bit instruction even though the same

; operation can be done by a 16-bit instruction

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 ≤

Can have any

value

Always. This is the default when no suffix is

specified.

Table 10-16. Condition code suffixes (Continued)

Suffix Flags Meaning