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133 lines
2.0 KiB
133 lines
2.0 KiB
4 years ago
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include "hardware.inc"
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section "home/serial.asm@hram", hram
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h_serial_len: dw
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h_serial_send_ptr: dw
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h_serial_recv_ptr: dw
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section "home/serial.asm@int58", rom0[$58]
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push af
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push hl
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push bc
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push de
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jp serial_shift_int
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section "home/serial.asm", rom0
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serial_shift_int:
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call serial_shift
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pop de
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pop bc
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pop hl
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pop af
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reti
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serial_end:
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serial_shift:
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ldh a, [h_serial_len + 0]
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ld c, a
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ldh a, [h_serial_len + 1]
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ld b, a
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; End early if we're done
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or c
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ret z
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ldh a, [h_serial_recv_ptr + 0]
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ld e, a
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ldh a, [h_serial_recv_ptr + 1]
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ld d, a
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; Store the last received byte
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or e
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jr z, .no_recv
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ldh a, [r_sb]
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ld [de], a
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inc de
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.no_recv
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; We've transferred an entire byte in both directions
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dec bc
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ldh a, [h_serial_send_ptr + 0]
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ld l, a
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ldh a, [h_serial_send_ptr + 1]
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ld h, a
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; fallthrough
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serial_queue:
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; If the length is 0, not much should be done
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ld a, b
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or c
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jr z, .empty
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ld a, h
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or l
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ld a, -1
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jr z, .no_send
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ld a, [hli]
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.no_send
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ldh [r_sb], a
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ldh a, [r_sc]
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set r_sc_start_f, a
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jr .store
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.empty
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ldh a, [r_sc]
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res r_sc_start_f, a
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.store
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ldh [r_sc], a
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ld a, c
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ldh [h_serial_len + 0], a
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ld a, b
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ldh [h_serial_len + 1], a
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ld a, e
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ldh [h_serial_recv_ptr + 0], a
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ld a, d
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ldh [h_serial_recv_ptr + 1], a
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ld a, l
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ldh [h_serial_send_ptr + 0], a
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ld a, h
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ldh [h_serial_send_ptr + 1], a
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ret
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serial_finished::
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; ret: z if done, nz if not done
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ldh a, [r_sc]
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bit r_sc_start_f, a
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ret
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serial_transfer::
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; hl: Source buffer
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; de: Destination buffer
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; bc: Size
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; ret: nz if previous transfer is still in transit
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call serial_finished
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ret nz
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jp serial_queue
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serial_init_master::
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ld a, 1
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db $fe ; CP A, n8
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serial_init_slave::
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xor a
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; fallthrough
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serial_init:
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ldh [r_sc], a
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ldh a, [r_ie]
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set r_int_serial_f, a
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ldh [r_ie], a
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ret
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