1 files changed, 113 insertions, 0 deletions
diff --git a/src/crt0.asm b/src/crt0.asm
new file mode 100644
index 0000000..71f35c5
--- /dev/null
+++ b/src/crt0.asm
@@ -0,0 +1,113 @@
+#include <zeta/zeta.h>
+
+	.module crt0
+	.globl	_main
+
+	.area	_HEADER (ABS)
+	;; Reset vector
+	.org 	0x0000
+	ld      sp, #0x00
+	xor     a
+	ld      i, a
+	jp      init
+	;; ISR table
+	.org    0x0010
+_ctc0_isr_ptr:
+	.dw     #0
+_ctc1_isr_ptr:
+	.dw     #0
+_ctc2_isr_ptr:
+	.dw     #0
+	.globl  _ctc3_isr_ptr
+_ctc3_isr_ptr:
+	.dw     #_ctc3_isr
+	.globl  _rx_isr_ptr
+_rx_isr_ptr:
+	.dw     #_rx_isr
+	;; Init code
+init:
+	;; Init windows
+	xor     a
+	out     (WIN_0_CTRL), A
+	ld      a, #0x80
+	out     (WIN_1_CTRL), A
+	ld      a, #0x81
+	out     (WIN_2_CTRL), A
+	ld      a, #0x82
+	out     (WIN_3_CTRL), A
+
+	;; Enable extended memory
+	ld      a, #0x01
+	out     (#0x84), A
+
+	;; Disable PIO interrupts
+	ld      a, #0x07
+	out     (PORT_A_CTRL), a
+	ld      a, #0x07
+	out     (PORT_B_CTRL), a
+
+	ld  a, #PIO_MODE_3
+	out (#PORT_A_CTRL), a
+	xor a
+	out (#PORT_A_CTRL), a
+
+
+	ld  a, #1
+	ld  b, #1
+2$:
+	xor b
+	out (PORT_A_DATA), a
+	jr  2$
+
+	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