Datasheet

82
11011B–ATARM–21-Feb-12
SAM3N
10.11.4.2 LSR
Logical shift right by n bits moves the left-hand 32-n bits of the register Rm, to the right by n
places, into the right-hand 32-n bits of the result. And it sets the left-hand n bits of the result to 0.
See Figure 10-5.
You can use the LSR #n operation to divide the value in the register Rm by 2
n
, if the value is
regarded as an unsigned integer.
When the instruction is LSRS or when LSR #n is used in Operand2 with the instructions MOVS,
MVNS, ANDS, ORRS, ORNS, EORS, BICS, TEQ or TST, the carry flag is updated to the last bit
shifted out, bit[n-1], of the register Rm.
•If n is 32 or more, then all the bits in the result are cleared to 0.
•If n is 33 or more and the carry flag is updated, it is updated to 0.
Figure 10-5. LSR #3
10.11.4.3 LSL
Logical shift left by n bits moves the right-hand 32-n bits of the register Rm, to the left by n
places, into the left-hand 32-n bits of the result. And it sets the right-hand n bits of the result to 0.
See Figure 10-6 on page 82.
You can use he LSL #n operation to multiply the value in the register Rm by 2
n
, if the value is
regarded as an unsigned integer or a two’s complement signed integer. Overflow can occur
without warning.
When the instruction is LSLS or when LSL #n, with non-zero n, is used in Operand2 with the
instructions MOVS, MVNS, ANDS, ORRS, ORNS, EORS, BICS, TEQ or TST, the carry flag is
updated to the last bit shifted out, bit[32-n], of the register Rm. These instructions do not affect
the carry flag when used with LSL #0.
•If n is 32 or more, then all the bits in the result are cleared to 0.
•If n is 33 or more and the carry flag is updated, it is updated to 0.
Figure 10-6. LSL #3
31 10
Carry
Flag
...
000
2345
31 10
Carry
Flag
...
000
2345