[mubios] Have IRQ0 maintain the BIOS clock, and implement INT 1Ah AH=00h.

Signed-off-by: Richard Qin <richard.qin.x@gmail.com>

1 files changed, 50 insertions, 0 deletions

diff --git a/mubios/arch/interrupt.S b/mubios/arch/interrupt.S
new file mode 100644
index 0000000..7cb3f4b
--- /dev/null
+++ b/mubios/arch/interrupt.S
@@ -0,0 +1,50 @@
+# RCC-Project
+#
+# Copyright (C) 2026 Richard Qin
+#
+# This file is part of RCC-Project.
+#
+# RCC-Project is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free
+# Software Foundation; either version 3 of the License, or (at your option) any
+# later version.
+#
+# RCC-Project is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# RCC-Project; see the file COPYING.  If not see
+# <http://www.gnu.org/licenses/>.
+
+	.intel_syntax noprefix
+	.code16
+
+	.section .text16.irq, "ax"
+
+	.global int1a_entry
+	.type int1a_entry, @function
+
+int1a_entry:
+	cmp ah, 0x00
+	jne int1a_return
+
+	push ds
+	push bx
+
+	xor bx, bx
+	mov ds, bx
+
+	mov bx, 0x046C
+	mov cx, word ptr [bx + 2]
+	mov dx, word ptr [bx]
+
+	mov al, byte ptr [0x0470]
+	mov byte ptr [0x0470], 0
+	mov ah, 0x00
+
+	pop bx
+	pop ds
+
+int1a_return:
+	iret