PM0215 datasheet(37/91 Pages) STMICROELECTRONICS

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PM0215

The STM32 Cortex-M0 instruction set

Doc ID 022979 Rev 1

37/91

ASR

Arithmetic 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 copies the original bit[31] of the

You can use the ASR operation to divide the signed value in the register Rm by 2n, with the

result being rounded towards negative-infinity.

When the instruction is ASRS, the carry flag is updated to the last bit shifted out, bit[n-1], of

the register Rm.

Note:

If n is 32 or more, all the bits in the result are set to the value of bit[31] of Rm.

2If n is 32 or more and the carry flag is updated, it is updated to the value of bit[31] of Rm.

Figure 10.

ASR#3

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 11).

You can use the LSR #n operation to divide the value in the register Rm by 2n, if the value is

regarded as an unsigned integer.

When the instruction is LSRS, the carry flag is updated to the last bit shifted out, bit[n-1], of

the register Rm.

Note:

If n is 32 or more, then all the bits in the result are cleared to 0.

2If n is 33 or more and the carry flag is updated, it is updated to 0.

Figure 11.

LSR#3

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PM0215 数据表(PDF) 37 Page - STMicroelectronics