ARM Cortex-M3 Instrukcja Użytkownika Pobierz pdf (Strona 20)

Conditional Execution

ITTET EQ

Inst 1

Inst 2

Inst 3

Inst 4



–

Then (IT) instruction added (16 bit)



Up to 3 additional “then” or “else” conditions maybe specified (T or E)



Makes up to 4 following instructions conditional



Any normal ARM condition code can be used



bit instructions in block do not affect condition code flags



Apart from comparison instruction



32 bit instructions may affect flags (normal rules apply

)



Current “if

then status” stored in CPSR



Conditional block maybe safely interrupted and returned to



Must NOT branch into or out of ‘if

then’ block

MOVEQ

ADDEQ

SUBNE

ORREQ

1 2 ... 15 16 17 18 19 20 21 22 23 24 25 ... 40 41

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ARM Cortex-M3 Instrukcja Użytkownika Strona 20