From ad2623d8c4bc51638343ae9a628f8647ff558155 Mon Sep 17 00:00:00 2001
From: Thomas Albers <thomas@thomaslabs.org>
Date: Mon, 14 Aug 2023 10:47:54 +0200
Subject: Initial commit

---
 stn/crt0.asm | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 stn/crt0.asm

(limited to 'stn/crt0.asm')

diff --git a/stn/crt0.asm b/stn/crt0.asm
new file mode 100644
index 0000000..2fdef59
--- /dev/null
+++ b/stn/crt0.asm
@@ -0,0 +1,66 @@
+#include <zeta.h>
+
+	.module crt0
+	.globl	_main
+
+	.area	_HEADER (ABS)
+	;; Reset vector
+	.org 	0x4000
+    ld      SP, #0x00
+    jp      init
+    ;; ISR table
+
+    ;; Init code
+init:
+    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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