SBRS – Skip if Bit in Register is Set

Operation:

(i)

If Rr(b) = 1 then PC ←

PC + 2 (or 3) else PC ←

PC + 1

Syntax:

Operands:

Program Counter:

(i)

SBRS Rr,b

0 ≤

r ≤

31, 0 ≤ b ≤

7

PC ← PC + 1, Condition false - no skip

PC ← PC + 2, Skip a one word instruction

PC ← PC + 3, Skip a two word instruction

16-bit Opcode:

1111

111r

rrrr

0bbb

Status Register (SREG) and Boolean Formula:

I

T

H

S

V

N

Z

C

–

–

–

–

–

–

–

–

Example:

sub

r0,r1

; Subtract r1 from r0

sbrs

r0,7

; Skip if bit 7 in r0 set

neg

r0

; Only executed if bit 7 in r0 not set

nop

; Continue (do nothing)

Words:

1 (2 bytes)

Cycles:

1 if condition is false (no skip)

2 if condition is true (skip is executed) and the instruction skipped is 1 word

3 if condition is true (skip is executed) and the instruction skipped is 2 words

Operation:

(i)

C ← 1

Syntax:

Operands:

Program Counter:

(i)

SEC

None

PC ← PC + 1

16-bit Opcode:

1001

0100

0000

1000

Status Register (SREG) and Boolean Formula:

I

T

H

S

V

N

Z

C

–

–

–

–

–

–

–

1

sec

;

Set Carry Flag

adc

r0,r1 ;

r0=r0+r1+1

Operation:

(i)

H ← 1

Syntax:

Operands:

Program Counter:

(i)

SEH

None

PC ← PC + 1

16-bit Opcode:

1001

0100

0101

1000

Status Register (SREG) and Boolean Formula:

I

T

H

S

V

N

Z

C

–

–

1

–

–

–

–

–

seh

; Set Half Carry Flag

Operation:

(i)

I ← 1

Syntax:

Operands:

Program Counter:

(i)

SEI

None

PC ← PC + 1

16-bit Opcode:

1001

0100

0111

1000

Status Register (SREG) and Boolean Formula:

I

T

H

S

V

N

Z

C

1

–

–

–

–

–

–

–

sei

; set global

interrupt

enable

sleep

;

enter sleep, waiting

for interrupt

;

note: will

enter sleep before any pending interrupt(s)

Words:

1 (2 bytes)

Cycles:

1