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#3943 Rabbit 4000 mode 10 page 0x7f ex instruction issue

open
nobody
R4K (4)
other
5
2026-03-13
2026-03-12
Philipp Klaus Krause
No

In mode 10, I see the ex bc, hl instruction just copy bc into hl, leaving the value in bc unchanged. This needs to be looked into further before we can use the instruction in codegen.

P.S.: Further testing indicates that similarly, ex jk, hl just copies jk into hl.

1 Attachments
main.c

Discussion

  • Philipp Klaus Krause

    Philipp Klaus Krause - 2026-03-12
    • summary: Rabbit 4000 ex bc, hl issue --> Rabbit 4000 ex bc, hl and ex jk, hl issue
    • Description has changed:

    Diff:

    --- old
+++ new
@@ -1 +1,3 @@
-In mode 10, I see the `ex bc, hl` instruction just copy bc into hl, leaving the value in bc unchanged. This needs to be looked into further before we can use the instruction in codegen.
+In mode 10, I see the `ex bc, hl` instruction just copy `bc` into `hl`, leaving the value in `bc` unchanged. This needs to be looked into further before we can use the instruction in codegen.
+
+P.S.: Further testing indicates that similarly, `ex jk, hl` just copies `jk` into `hl`.
     

  • Philipp Klaus Krause

    Philipp Klaus Krause - 2026-03-13
     

  • Philipp Klaus Krause

    Philipp Klaus Krause - 2026-03-13

    Testing further, it looks like all 3 ex instruction on page 0x7f in mode 10 copy one operand into the other. Maybe some other location gets written instead that I didn't check, though.

    ex bc, hl looks like ld hl, bc
    ex jk, hl looks like ld hl, jk
    ex jkhl, bcde looks like ld jkhl, bcde

     

  • Philipp Klaus Krause

    Philipp Klaus Krause - 2026-03-13
    • labels: --> R4K
    • summary: Rabbit 4000 ex bc, hl and ex jk, hl issue --> Rabbit 4000 mode 10 page 0x7f ex instruction issue
     

  • Philipp Klaus Krause

    Philipp Klaus Krause - 2026-03-13

    Testing further, it looks like all 3 ex instruction on page 0x7f in mode 10 copy one operand into the other. Maybe some other location gets written instead that I didn't check, though.

    ex bc, hl looks like ld hl, bc
    ex jk, hl looks like ld hl, jk
    ex khl, bcde looks like ld jkhl, bcde

     

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