PM0214 datasheet(145/245 Pages) STMICROELECTRONICS

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PM0214

The STM32 Cortex-M4 instruction set

244

Other restrictions when using an IT block are:

•

a branch or any instruction that modifies the PC must either be outside an IT block or

must be the last instruction inside the IT block. These are:

–

ADD PC, PC, Rm

–

MOV PC, Rm

–

B, BL, BX, BLX

–

any LDM, LDR, or POP instruction that writes to the PC

–

TBB and TBH

•

Do not branch to any instruction inside an IT block, except when returning from an

exception handler

•

All conditional instructions except Bcond must be inside an IT block. Bcond can be

either outside or inside an IT block but has a larger branch range if it is inside one

•

Each instruction inside the IT block must specify a condition code suffix that is either

the same or logical inverse as for the other instructions in the block.

Your assembler might place extra restrictions on the use of IT blocks, such as prohibiting the

use of assembler directives within them.

Condition flags

This instruction does not change the flags.

Example

ITTE

; Next 3 instructions are conditional

ANDNE

R0, R0, R1

; ANDNE does not update condition flags

ADDSNE R2, R2, #1

; ADDSNE updates condition flags

MOVEQ

R2, R3

; Conditional move

CMP

R0, #9

; Convert R0 hex value (0 to 15) into ASCII

; ('0'-'9', 'A'-'F')

ITE

; Next 2 instructions are conditional

ADDGT

R1, R0, #55

; Convert 0xA -> 'A'

ADDLE

R1, R0, #48

; Convert 0x0 -> '0'

; IT block with only one conditional instruction

ADDGT

R1, R1, #1

; Increment R1 conditionally

ITTEE

; Next 4 instructions are conditional

MOVEQ

R0, R1

; Conditional move

ADDEQ

R2, R2, #10

; Conditional add

ANDNE

R3, R3, #1

; Conditional AND

BNE.W

dloop

; Branch instruction can only be used in the last

; instruction of an IT block

; Next instruction is conditional

ADD

R0, R0, R1

; Syntax error: no condition code used in IT block

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