How to access undocumented z80-instructions in SDCC (sdasz80)?

Hero (578)

22-05-2022, 21:46

Good news! Philipp Klaus Krause just informed me that using the later snapshot builds allows the use of the command line parameter:

--allow-undocumented-instructions

and it works. I just found my generated asm having iyh and iyl.

As for what is supported I quote:

Quote:

SDCC will use any undocumented instruction that is an official instruction in the eZ80 to access iyl and iyh.
sdasz80 / inline asm allow more.

Note: Official 4.2 is not recent enough.

By aoineko

Champion (440)

22-05-2022, 22:04

What a timing! I just added Pletter support to MSXgl yesterday and ran into the problem of undocumented instruction support.
In the code, I replaced these instructions by their equivalent in raw data, but I left them as comments... just in case. ^^
Even if I personally won't use undocumented instructions, it is still useful to include third party code.
I hope they will add a pragma to enable this option only on some source code.

By aoineko

Champion (440)

12-06-2022, 19:10

@Bengalack I can't found information about how to use undocumented instructions with SDCC.
I guess --allow-undocumented-instructions is a command line parameter for SDCC and concerns the assembly code generated from the C sources.
However, I did not find how to use it with sdasz80 and/or with the inline assembler.

.z80
.allow_undocumented

...generates an error.

PS: I got the last snapshot (build 13495).

By geijoenr

Champion (311)

12-06-2022, 19:43

I had the same problem, if you use .z180 instead of .z80 it does work.

By Bengalack

Hero (578)

12-06-2022, 23:48

I use .allow_undocumented (only) in the asm-file with sdasz80 without problems. But for c-code, I use the command-line-parameter (and "-mz80"). I guess the functionality is so new, it didn't reach the documentation yet.

By gdx

Enlighted (5473)