Freescale-semiconductor StarCore SC140 Bedienungsanleitung Seite 477

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EI
SC140 DSP Core Reference Manual A-163
E-J
EI Enable Interrupts (AGU) EI
Description
Status and Conditions that Affect Instruction
Status and Conditions Changed by Instruction
Example
ei
Instruction Formats and Opcodes
Operation Assembler Syntax
0 DI
EI
EI
Clears the DI bit in the status register to enable interrupts. The EI instruction and its counterpart, the DI
instruction, can be used to delimit a non-interruptible code sequence. For example, a non-interruptible
read-modify-write sequence of execution sets can be written like this:
DI read
modify
EI write
Where read, modify, and write represent instruction(s). This instruction can appear only once in an
execution set. The effect of EI may not be immediate. That is, a pending interrupt may not be serviced as
the first execution set immediately after this instruction because of pipeline effects.
Register Address Bit Name Description
SR[18] EXP Determines execution working mode.
Register Address Bit Name Description
SR[19] DI Clears disable interrupt bit.
Register/Memory Address Before After
SR
$EC0000 $E40000
Instruction Words Cycles Type Opcode
15 8 7 0
EI 1 1 4 1001111101111100
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