From 9ff2033e936689135210989a5fee057a4a13527e Mon Sep 17 00:00:00 2001 From: Miquel Sabaté Solà Date: Thu, 13 Mar 2025 22:52:49 +0100 Subject: Add a title and a main screens MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This commit adds the skeleton for having a title and a main screen. For now the title menu doesn't do much, as the selection is simply ignored, but at least it already knows how to cycle between these two states. Signed-off-by: Miquel Sabaté Solà --- include/asm.s | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) create mode 100644 include/asm.s (limited to 'include/asm.s') diff --git a/include/asm.s b/include/asm.s new file mode 100644 index 0000000..67b195c --- /dev/null +++ b/include/asm.s @@ -0,0 +1,22 @@ +;; Jump And Link: jump to subroutine but use the return address that the caller +;; had whenever the given subroutine runs `rts`. In other words, "link" the +;; return address from the caller to the callee. +;; +;; This is in practice the same as using `jmp` but it bears the semantic +;; connotation of the `jsr` one. That is, instead of this: +;; +;; jsr subroutine +;; rts +;; +;; It's more adviseable to do the following for better stack management: +;; +;; jmp subroutine +;; +;; That being said, the `jmp` instruction is also used in many other contexts, +;; and so sometimes it's needed to clarify that: "no, I have not messed up, +;; using `jmp` here instead of `jsr` is deliberate". Hence, instead of adding a +;; comment every time this small optimization is being done, use this +;; pseudo-instruction. +.macro JAL ADDR + jmp ADDR +.endmacro -- cgit v1.2.3