Prefixed instructions (Z80)

[elpekos]

Z80 processor has a variable length of instructions : 1 byte to 4 bytes with 4 prefix whose can be mixed.
Do you plan to implement this kind of decoder ?

[FRoith]

Since this decoder is intended for decoding fixed width signals in, for example, surfer, and real waveforms do not have variable length signals, this is not planned.

The two ways you have to solve it, is to either have a decoder toml for each of the byte sizes, which would not work for waveforms, since the signals there always have the same width, or create toml files which match the "smaller" instructions in the 4 bytes (see toml/RV32C-lower.toml for example)

[elpekos]

I understand, variable length is not adequate and Z80 should be treated as 8 bits width. Maybe having a variable which keeps the previous value and the ability to switch the table according this value ? T.

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Le 19 juin 2026 à 21:15, FRoith ***@***.***> a écrit : FRoith left a comment (ics-jku/instruction-decoder#45) <#45 (comment)> Since this decoder is intended for decoding fixed width signals in, for example, surfer, and real waveforms do not have variable length signals, this is not planned. The two ways you have to solve it, is to either have a decoder toml for each of the byte sizes, which would not work for waveforms, since the signals there always have the same width, or create toml files which match the "smaller" instructions in the 4 bytes (see toml/RV32C-lower.toml <x-msg://9/toml/RV32C-lower.toml> for example) — Reply to this email directly, view it on GitHub <#45?email_source=notifications&email_token=AI7P7TLPSWF5SQXGGBAQQQD5AWGNDA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTINZVGQYTGOBWGA2KM4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2KYZTPN52GK4S7MNWGSY3L#issuecomment-4754138604>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AI7P7TJ4BTVXFCJ6UV6A6ML5AWGNDAVCNFSNUABFKJSXA33TNF2G64TZHM4DAMJZGYYTGNBWHNEXG43VMU5TINZQGIZTQOJVG442C5QC>. Triage notifications, keep track of coding agent tasks and review pull requests on the go with GitHub Mobile for iOS <https://github.com/notifications/mobile/ios/AI7P7TIW5Z5MAMN7J6B3I4T5AWGNDA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTINZVGQYTGOBWGA2KM4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2KUZTPN52GK4S7NFXXG> and Android <https://github.com/notifications/mobile/android/AI7P7TMFJHBXVHXSBN7P4TL5AWGNDA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTINZVGQYTGOBWGA2KM4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2K4ZTPN52GK4S7MFXGI4TPNFSA>. Download it today! You are receiving this because you authored the thread.