NORMAL PROCESSING STATE

Note 1: INST 3 may be executed at that point only if the preceding instruction (INST 2) was a single-word instruction.

Note 2: II=Interrupt instruction from maskable interrupt.

The following program flow will not occur because the new interrupt mask level becomes effective after a pipeline latency of four instruction cycles:

 

 

ORI #03,MR

;Disable interrupts.

INST 1

 

INST 2

 

INST 3

 

INST 4

 

II

;Interrupts disabled.

II+1

;Interrupts disabled.

1. Program flow without interrupts after interrupts are re-enabled:

ANDI #00,MR ;Enable interrupts INST 1

INST 2

INST 3 INST 4

2. Program flow with interrupts after interrupts are re-enabled:

 

 

ANDI #00,MR

;Enable interrupts

INST 1

;Uninterruptable

INST 2

;Uninterruptable

INST 3

;II fetched

INST 4

;II+1 fetched

II

 

II+1

 

 

 

MOTOROLA

PROCESSING STATES

7 - 7

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Image 134
Motorola DSP56000, 24-Bit Digital Signal Processor manual Inst Inst 3 Inst, Andi #00,MR