From de725da74db5cba0f9bfd0755269e1683423d87b Mon Sep 17 00:00:00 2001
From: user <user@clank>
Date: Wed, 15 Jul 2026 23:44:28 +0200
Subject: gbos scaffold: working cooperative microkernel (verified ABAB in
 emulator)

- fix ClearKernelRAM clobbering the kernel stack (only clear $C000-$CBFF)
- fix SyscallTrap clobbering DE (buffer arg) during table dispatch
- README: run via ~/dev/gbc --headless; note bring-up bugs
---
 src/tty.asm | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
 create mode 100644 src/tty.asm

(limited to 'src/tty.asm')

diff --git a/src/tty.asm b/src/tty.asm
new file mode 100644
index 0000000..d2c1234
--- /dev/null
+++ b/src/tty.asm
@@ -0,0 +1,15 @@
+; =============================================================================
+; tty.asm - console output over the serial port (emulator debug channel).
+; A real gbos would render to VRAM; serial is a zero-VRAM stub that shows up
+; in emulator serial logs (bgb/SameBoy) and on link hardware.
+; =============================================================================
+INCLUDE "include/gbos.inc"
+
+SECTION "tty", ROM0
+
+; PutChar - A = character. Push to serial data and kick a transfer.
+PutChar::
+    ld [rSB], a
+    ld a, $81               ; start transfer, internal clock
+    ld [rSC], a
+    ret
-- 
cgit v1.3.1-sl0p