Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet

101

SAM4S Series [DATASHEET]

Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14

A conditional execution can be used with the IT instruction to reduce the number of branch instructions in code.

 also shows the relationship between condition code suffixes and the N, Z, C, and V flags.

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

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

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, the user 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 the user specifies an instruction width suffix and the assembler cannot generate an instruction encoding of the 

requested width, it generates an error. 

Note:

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. 

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.