From d46862a5bd2319c595b11427f781201ca063d194 Mon Sep 17 00:00:00 2001
From: Thomas Albers Raviola <thomas@thomaslabs.org>
Date: Tue, 3 Dec 2024 21:45:47 +0100
Subject: Add bootloader

---
 boot/crt0.asm | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 boot/crt0.asm

(limited to 'boot/crt0.asm')

diff --git a/boot/crt0.asm b/boot/crt0.asm
new file mode 100644
index 0000000..09e4166
--- /dev/null
+++ b/boot/crt0.asm
@@ -0,0 +1,79 @@
+#include <hardware.h>
+    .module crt0
+    .globl  _main
+
+	.area	_HEADER (ABS)
+    .org    0x8000
+start:
+    di
+    ld      a, #0x80
+    ld      i, a
+    ld      sp, #0x0000
+    jr      main
+    .org    0x8010
+_ctc0_isr_ptr::
+    .dw     #0
+_ctc1_isr_ptr::
+    .dw     #_ctc1_isr
+_ctc2_isr_ptr::
+    .dw     #0
+_ctc3_isr_ptr::
+    .dw     #0
+_port_a_isr_ptr::
+    .dw     #0
+_port_b_isr_ptr::
+    .dw     #0
+_rx_isr_ptr::
+    .dw     #_rx_isr
+main:
+    call	gsinit
+	call	_main
+1$:
+	halt
+	jr	1$
+
+	;; Ordering of segments for the linker.
+	.area	_HOME
+	.area	_CODE
+	.area	_INITIALIZER
+	.area   _GSINIT
+	.area   _GSFINAL
+
+	.area	_DATA
+	.area	_INITIALIZED
+	.area	_BSEG
+	.area   _BSS
+	.area   _HEAP
+
+	.area   _CODE
+
+	.area   _GSINIT
+gsinit:
+	;; Default-initialized global variables.
+    ld      bc, #l__DATA
+    ld      a, b
+    or      a, c
+    jr      Z, zeroed_data
+    ld      hl, #s__DATA
+    ld      (hl), #0x00
+    dec     bc
+    ld      a, b
+    or      a, c
+    jr      Z, zeroed_data
+    ld      e, l
+    ld      d, h
+    inc     de
+    ldir
+zeroed_data:
+	;; Explicitly initialized global variables.
+	ld	bc, #l__INITIALIZER
+	ld	a, b
+	or	a, c
+	jr	Z, gsinit_next
+	ld	de, #s__INITIALIZED
+	ld	hl, #s__INITIALIZER
+	ldir
+
+gsinit_next:
+	.area   _GSFINAL
+	ret
-- 
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