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DMD 5620 Core Notes

About

This document contains miscellaneous development notes taken while working on devleopment.

Features

CPU Idle Loop Detection

There are several interesting blocks that look like idle loops. Ideally, we want to detect these loops and just idle the CPU until the next interrupt is likely to occur.

Idle Loop Example 1

This tight loop occurs early on before startup is complete, and only exits via interrupt which sets some value in *$0x71a79c.

  [0000678d] MOVH     *$0x71a79c,%r0
  [00006795] CMPW     %r1,%r0
  [00006798] BLB

Idle Loop Example 2

This occurs later on after startup is complete. It continuously calls the function at 0x715c.

  [0000068c] BITW     %r0,$0x16
  [0000068f] BEB
  [00000659] TSTB     0x6293186
  [0000065f] BNEB
  [00000661] TSTW     64(%r9)
  [00000664] BNEB
  [0000715c] CALL     (%r12),0x29020
  [0000715c] SAVE     %r9
  [0000715e] MOVW     $0x71c590,%r1
  [00007161] ADDW3    $0x71c590,0x1096,%r0
  [00007169] TSTH     (%r0)
  [0000716b] BLEB
  [00007170] MOVW     *$0x719024,%r0
  [00007177] MOVW     (%r0),%r0
  [0000717a] TSTH     52(%r0)
  [0000717d] BLEB
  [00007182] MOVW     %r1,%r0
  [00007185] RESTORE  %r9
  [0000068c] RET

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