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; vector table fields
@let vector_table 0x10
@let vt_ISR0 0x10 ; ISR0
@let vt_ISR1 0x11 ; ISR1
@let vt_ISR2 0x12 ; ISR2
@let vt_ISR3 0x13 ; ISR3
@let vt_stack_addr 0x14 ; Stack address
@let vt_term_pp_addr 0x15 ; Terminal peripheral address
@let vt_kb_pp_addr 0x16 ; Keyboard peripheral address
@let vt_gr_mode_addr 0x17 ; Graphics mode setting address
; memory segments
@let charmem_segment 0x0100
@let stack_segment 0x8000
@let mmio_segment 0xE000
@let terminal_addr 0xE000
@let keyboard_addr 0xE001
@let gr_mode_addr 0xE002
@let sprite_mem 0xE800
; graphics mode settings
@let gr_disabled_mode 0b00
@let gr_text_mode 0b01
@let gr_sprite_mode 0b10
@address vector_table
keyboard_isr ; 0x10
hlt_isr ; 0x11
hlt_isr ; 0x12
hlt_isr ; 0x13
stack_segment ; 0x14
terminal_addr ; 0x15
keyboard_addr ; 0x16
gr_mode_addr ; 0x17
@label hlt_isr
ldi 0x55 RE
hlt
@label keyboard_isr
stack_stash RA RB
ldi vt_kb_pp_addr RA ; RA := Keyboard peripheral address pointer
ldr RA RA ; RA := Keyboard peripheral address deref
ldr RA RA ; RA := <16-bit keyboard character code> from MMIO register
ldi vt_term_pp_addr RB ; RB := Terminal peripheral address pointer
ldr RB RB ; RB := Terminal peripheral address deref
str RA RB ; terminal <- character code (ASCII?)
mov RA RE ; RE := character code (for debugging)
stack_restore RA RB
rti
@label program_segment
; define short prelude that sets up vital instructions
; NOTE: must be shorter than the vector table offset
@address 0x0
; set up stack pointer to point to beginning of stack segment
ldi vt_stack_addr RA
ldr RA RF
jpi program_segment
@address program_segment
; set graphics mode to disabled
set_graphics_mode gr_disabled_mode
; jump to main (user defined)
jpi main
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