From f806786bd3d0a81ec844aaa90e08c04c32893c20 Mon Sep 17 00:00:00 2001 From: Virgil Dupras Date: Thu, 17 Oct 2019 15:52:59 -0400 Subject: [PATCH] zasm: document lack of support for undocumented instructions --- apps/zasm/README.md | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/apps/zasm/README.md b/apps/zasm/README.md index 1b6a60c..906f4c8 100644 --- a/apps/zasm/README.md +++ b/apps/zasm/README.md @@ -152,4 +152,11 @@ allowed. An included file cannot have an `.inc` directive. in the argument in the currently active filesystem and outputs its contents directly. +## Undocumented instructions + +`zasm` doesn't support undocumented instructions such as the ones that involve +using `IX` and `IY` as 8-bit registers. We used to support them, but because +this makes our code incompatible with Z80-compatible CPUs such as the Z180, we +prefer to avoid these in our code. + [libz80]: https://github.com/ggambetta/libz80