diff options
Diffstat (limited to 'crt0.asm')
| -rw-r--r-- | crt0.asm | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/crt0.asm b/crt0.asm new file mode 100644 index 0000000..567ab47 --- /dev/null +++ b/crt0.asm @@ -0,0 +1,93 @@ +#include <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: + xor A + ;; Enable extended memory + out (WIN_0_CTRL), A + ld A, #0b00100000 + out (WIN_1_CTRL), A + ld A, #0b01000000 + out (WIN_2_CTRL), A + ld A, #0b01100000 + out (WIN_3_CTRL), A + + ld A, #SREG_EXT_MEM + out (SREG_CTRL), A + + 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 |