Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Hoja De Datos

 91

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

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 automat-
ically 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.