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@let SP RH
; memory segments
@let stack_segment 0x8000
@let heap_segment 0xE7EF ; grows down from 0xE7EF until SP
@let mmio_segment 0xE7F0
@let terminal_addr 0xE7F0
@let keyboard_addr 0xE7F1
@let gr_mode_addr 0xE7F2
@let iset_addr 0xE7F3
@let sprite_mem 0xE800
@let text_mem 0xF800 ; to 0xFFFF
; note: sprite memory & text memory can use the same space
; since they are never used at the same time
; graphics mode settings
@let gr_disabled_mode 0b00
@let gr_text_mode 0b01
@let gr_sprite_mode 0b10
; 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
@let vt_sprite_mem 0x18 ; Sprite memory address
@let vt_text_mem 0x19 ; Text memory buffer address
@let vt_iset_addr 0x1A ; Interrupt set/clear address
@address vector_table
no_op_isr ; 0x10
no_op_isr ; 0x11
no_op_isr ; 0x12
no_op_isr ; 0x13
stack_segment ; 0x14
terminal_addr ; 0x15
keyboard_addr ; 0x16
gr_mode_addr ; 0x17
sprite_mem ; 0x18
text_mem ; 0x19
iset_addr ; 0x1A
@label no_op_isr
rti
; Define data segment location to this address
; Programs can use `@data label value` to inject data here
@label data_segment
@data_segment
; Example ISR for keyboard to terminal
; @label keyboard_to_terminal_isr
; spu RA
; spu 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)
; spo RB
; spo RA
; 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 SP
jpi program_segment
@address program_segment
; set graphics mode to disabled
ldi vt_gr_mode_addr RA
ldr RA RA
ldi gr_disabled_mode RB
str RB RA
; jump to main (user defined)
jpi main
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