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December 29, 2020 20:26
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| ; Copyright 2020 Jonathan Foucher | |
| ; Permission is hereby granted, free of charge, to any person obtaining a copy of this software | |
| ; and associated documentation files (the "Software"), to deal in the Software without restriction, | |
| ; including without limitation the rights to use, copy, modify, merge, publish, distribute, | |
| ; sublicense, and/or sell copies of the Software, and to permit persons to whom the Software | |
| ; is furnished to do so, subject to the following conditions: | |
| ; The above copyright notice and this permission notice shall be included in all copies or | |
| ; substantial portions of the Software. | |
| ; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, | |
| ; INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR | |
| ; PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE | |
| ; FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR | |
| ; OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER | |
| ; DEALINGS IN THE SOFTWARE. | |
| DATA = $80 ; Data is in bit 7 of PORTA | |
| ; clock is on CA2 | |
| SHIFT = $1 | |
| ALT = $2 | |
| KB_STATE_START = $0 | |
| KB_STATE_DATA = $1 | |
| KB_STATE_PARITY = $2 | |
| KB_STATE_STOP = $3 | |
| KB_INIT_STATE_RESET = $0 | |
| KB_INIT_STATE_RESET_ACK = $1 | |
| KB_INIT_STATE_LEDS = $2 | |
| KB_INIT_STATE_LEDS_ACK = $3 | |
| KB_INIT_STATE_LEDS_DATA = $4 | |
| KB_INIT_STATE_LEDS_DATA_ACK = $5 | |
| LSHIFT_KEY = $12 | |
| RSHIFT_KEY = $59 | |
| TIMER_DELAY = $C4 | |
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| ; Copyright 2020 Jonathan Foucher | |
| ; Permission is hereby granted, free of charge, to any person obtaining a copy of this software | |
| ; and associated documentation files (the "Software"), to deal in the Software without restriction, | |
| ; including without limitation the rights to use, copy, modify, merge, publish, distribute, | |
| ; sublicense, and/or sell copies of the Software, and to permit persons to whom the Software | |
| ; is furnished to do so, subject to the following conditions: | |
| ; The above copyright notice and this permission notice shall be included in all copies or | |
| ; substantial portions of the Software. | |
| ; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, | |
| ; INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR | |
| ; PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE | |
| ; FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR | |
| ; OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER | |
| ; DEALINGS IN THE SOFTWARE. | |
| ps2_init: | |
| lda IER | |
| ora #$88 ;enable interrupt on neg transition on CB2 | |
| sta IER | |
| lda #0 | |
| sta PCR | |
| sta KB_TEMP | |
| sta KB_BIT | |
| sta KB_STATE | |
| sta to_send | |
| sta KB_PARITY | |
| sta KB_BUF_INDEX | |
| sta KB_BUF_INDEX_R | |
| sta KB_INIT_STATE | |
| sta ready | |
| sta ignore_next | |
| sta character | |
| sta init_trys | |
| cli ;enable interrupts | |
| ; jsr kb_reset | |
| ; jsr kb_leds | |
| ; jsr kb_leds_data | |
| ; jmp done_init | |
| lda #KB_INIT_STATE_RESET | |
| sta KB_INIT_STATE | |
| @wait: | |
| lda to_send | |
| bne @wait ; do nothing while sending | |
| ;jsr lcd_print | |
| ldx KB_INIT_STATE | |
| ;stx PORTA | |
| cpx #KB_INIT_STATE_RESET | |
| beq @do_reset | |
| cpx #KB_INIT_STATE_RESET_ACK | |
| beq @reset_ack | |
| cpx #KB_INIT_STATE_LEDS | |
| beq @do_leds | |
| cpx #KB_INIT_STATE_LEDS_ACK | |
| beq @leds_ack | |
| cpx #KB_INIT_STATE_LEDS_DATA | |
| beq @_do_leds_data | |
| cpx #KB_INIT_STATE_LEDS_DATA_ACK | |
| beq @_leds_data_ack | |
| ; beq @self_test_ok ; Wait for 256 loops with nothing. if still nothing, reset keyboard | |
| bra @wait ; nothing to show yet | |
| ;sta PORTA | |
| ; wait for keyboard self test (#$AA) | |
| @_leds_data_ack: | |
| jmp @leds_data_ack | |
| @_do_leds_data: | |
| jmp @do_leds_data | |
| @do_reset: ; ready is in A | |
| jsr kb_reset | |
| lda #KB_INIT_STATE_RESET_ACK ; next state should be an acknowledgment | |
| sta KB_INIT_STATE | |
| bra @wait | |
| @reset_ack: | |
| jmp done_init ; key board works after reset, so return here | |
| ; The below is not used, my keyboard is happy with just a reset and starts sending keypresses | |
| lda ready | |
| beq @reset_ack | |
| jsr binhex | |
| jsr lcd_print | |
| txa | |
| jsr lcd_print | |
| tya | |
| cmp #$FA ; keyboard ack | |
| beq @reset_ack_ok | |
| bra @wait | |
| @reset_ack_ok: | |
| lda #KB_INIT_STATE_LEDS ; next state should be sending the LEDS data | |
| sta KB_INIT_STATE | |
| stz ready | |
| jsr kb_leds | |
| bra @wait | |
| @do_leds: | |
| lda #KB_INIT_STATE_LEDS_ACK ; next state should be an acknowledgment | |
| sta KB_INIT_STATE | |
| jsr kb_leds | |
| jmp @wait | |
| @leds_ack: | |
| lda ready | |
| beq @leds_ack | |
| cmp #$FA ; keyboard ack | |
| beq @leds_ack_ok | |
| jmp @wait | |
| @leds_ack_ok: | |
| lda #KB_INIT_STATE_LEDS_DATA ; next state should be sending the LEDS data | |
| sta KB_INIT_STATE | |
| stz ready | |
| jmp @wait | |
| @do_leds_data: | |
| lda #KB_INIT_STATE_LEDS_DATA_ACK ; back to start | |
| sta KB_INIT_STATE | |
| jsr kb_leds_data | |
| jmp @wait | |
| @leds_data_ack: | |
| beq @leds_data_ack | |
| lda ready | |
| cmp #$FA ; keyboard ack | |
| beq done_init | |
| jmp @wait | |
| done_init: | |
| lda #0 | |
| sta DDRB | |
| sta ignore_next | |
| sta ready | |
| sta control_keys | |
| sta temp | |
| sta to_send | |
| sta ready | |
| sta character | |
| sta KB_TEMP | |
| sta KB_INIT_STATE | |
| sta KB_BIT | |
| sta KB_STATE | |
| sta KB_BUF_INDEX | |
| sta KB_BUF_INDEX_R | |
| cli ; enable interrupts again | |
| rts | |
| kb_reset: | |
| sei ;disable interrupts | |
| jsr prepare_send | |
| lda #$FF | |
| sta to_send | |
| cli ; enable interrupts | |
| @wait: | |
| lda to_send | |
| bne @wait | |
| rts | |
| kb_leds: | |
| sei ;disable interrupts | |
| jsr prepare_send | |
| lda #$ED | |
| sta to_send | |
| cli ; enable interrupts | |
| @wait: | |
| lda to_send | |
| bne @wait | |
| rts | |
| kb_leds_data: | |
| sei ;disable interrupts | |
| jsr prepare_send | |
| lda #$02 | |
| sta to_send | |
| cli ; enable interrupts | |
| @wait: | |
| lda to_send | |
| bne @wait | |
| rts | |
| prepare_send: | |
| pha | |
| phy | |
| ; ready to send, pull clock low for a while | |
| lda #$C0 | |
| sta PCR ;set CB2 low | |
| ;delay | |
| ldy #$80 | |
| jsr delay | |
| ; delay end | |
| ; pull data low now | |
| lda PORTB | |
| and #(~DATA & $FF) | |
| sta PORTB | |
| lda DDRB | |
| ora #DATA ;data as output to set it low | |
| sta DDRB | |
| ldy #$40 | |
| jsr delay | |
| lda #KB_STATE_DATA ; no start bit when sending | |
| sta KB_STATE | |
| ; release clock | |
| lda #0 | |
| sta to_send | |
| sta KB_PARITY | |
| sta PCR ;set CB2 to negative edge input | |
| ply | |
| pla | |
| rts | |
| reset_ps2: ; routine called during a timer interrupt to check | |
| pha | |
| ; if the elasped time since the last ps2 interrupt allows us to reset it | |
| lda time+3 | |
| cmp last_ps2_time+3 | |
| bcc @reset | |
| lda time+2 | |
| cmp last_ps2_time+2 | |
| bcc @reset | |
| lda time+1 | |
| cmp last_ps2_time+1 | |
| bcc @reset | |
| lda time | |
| adc #$1 | |
| cmp last_ps2_time | |
| bcc @reset | |
| @exit: | |
| pla | |
| rts | |
| @reset: | |
| lda #0 | |
| sta KB_TEMP | |
| sta KB_BIT | |
| sta KB_STATE | |
| sta KB_BUF_INDEX | |
| sta KB_BUF_INDEX_R | |
| beq @exit | |
| .include "ps2_irq.s" | |
| KB_BUF: .res 256 | |
| ASCIITBL: | |
| .byte $00 ; 00 no key pressed | |
| .byte $89 ; 01 F9 | |
| .byte $87 ; 02 relocated F7 | |
| .byte $85 ; 03 F5 | |
| .byte $83 ; 04 F3 | |
| .byte $81 ; 05 F1 | |
| .byte $82 ; 06 F2 | |
| .byte $8C ; 07 F12 | |
| .byte $00 ; 08 | |
| .byte $8A ; 09 F10 | |
| .byte $88 ; 0A F8 | |
| .byte $86 ; 0B F6 | |
| .byte $84 ; 0C F4 | |
| .byte $09 ; 0D tab | |
| .byte $60 ; 0E `~ | |
| .byte $8F ; 0F relocated Print Screen key | |
| .byte $03 ; 10 relocated Pause/Break key | |
| .byte $A0 ; 11 left alt (right alt too) | |
| .byte $00 ; 12 left shift | |
| .byte $E0 ; 13 relocated Alt release code | |
| .byte $00 ; 14 left ctrl (right ctrl too) | |
| .byte $71 ; 15 qQ | |
| .byte $31 ; 16 1! | |
| .byte $00 ; 17 | |
| .byte $00 ; 18 | |
| .byte $00 ; 19 | |
| .byte $7A ; 1A zZ | |
| .byte $73 ; 1B sS | |
| .byte $61 ; 1C aA | |
| .byte $77 ; 1D wW | |
| .byte $32 ; 1E 2@ | |
| .byte $A1 ; 1F Windows 98 menu key (left side) | |
| .byte $02 ; 20 relocated ctrl-break key | |
| .byte $63 ; 21 cC | |
| .byte $78 ; 22 xX | |
| .byte $64 ; 23 dD | |
| .byte $65 ; 24 eE | |
| .byte $34 ; 25 4$ | |
| .byte $33 ; 26 3# | |
| .byte $A2 ; 27 Windows 98 menu key (right side) | |
| .byte $00 ; 28 | |
| .byte $20 ; 29 space | |
| .byte $76 ; 2A vV | |
| .byte $66 ; 2B fF | |
| .byte $74 ; 2C tT | |
| .byte $72 ; 2D rR | |
| .byte $35 ; 2E 5% | |
| .byte $A3 ; 2F Windows 98 option key (right click, right side) | |
| .byte $00 ; 30 | |
| .byte $6E ; 31 nN | |
| .byte $62 ; 32 bB | |
| .byte $68 ; 33 hH | |
| .byte $67 ; 34 gG | |
| .byte $79 ; 35 yY | |
| .byte $36 ; 36 6^ | |
| .byte $00 ; 37 | |
| .byte $00 ; 38 | |
| .byte $00 ; 39 | |
| .byte $6D ; 3A mM | |
| .byte $6A ; 3B jJ | |
| .byte $75 ; 3C uU | |
| .byte $37 ; 3D 7& | |
| .byte $38 ; 3E 8* | |
| .byte $00 ; 3F | |
| .byte $00 ; 40 | |
| .byte $2C ; 41 ,< | |
| .byte $6B ; 42 kK | |
| .byte $69 ; 43 iI | |
| .byte $6F ; 44 oO | |
| .byte $30 ; 45 0) | |
| .byte $39 ; 46 9( | |
| .byte $00 ; 47 | |
| .byte $00 ; 48 | |
| .byte $2E ; 49 .> | |
| .byte $2F ; 4A /? | |
| .byte $6C ; 4B lL | |
| .byte $3B ; 4C ;: | |
| .byte $70 ; 4D pP | |
| .byte $2D ; 4E -_ | |
| .byte $00 ; 4F | |
| .byte $00 ; 50 | |
| .byte $00 ; 51 | |
| .byte $27 ; 52 '" | |
| .byte $00 ; 53 | |
| .byte $5B ; 54 [{ | |
| .byte $3D ; 55 =+ | |
| .byte $00 ; 56 | |
| .byte $00 ; 57 | |
| .byte $00 ; 58 caps | |
| .byte $00 ; 59 r shift | |
| .byte $0D ; 5A <Enter> | |
| .byte $5D ; 5B ]} | |
| .byte $00 ; 5C | |
| .byte $5C ; 5D \| | |
| .byte $00 ; 5E | |
| .byte $00 ; 5F | |
| .byte $00 ; 60 | |
| .byte $00 ; 61 | |
| .byte $00 ; 62 | |
| .byte $00 ; 63 | |
| .byte $00 ; 64 | |
| .byte $00 ; 65 | |
| .byte $08 ; 66 bkspace | |
| .byte $00 ; 67 | |
| .byte $00 ; 68 | |
| .byte $31 ; 69 kp 1 | |
| .byte $2f ; 6A kp / converted from E04A in code | |
| .byte $34 ; 6B kp 4 | |
| .byte $37 ; 6C kp 7 | |
| .byte $00 ; 6D | |
| .byte $00 ; 6E | |
| .byte $00 ; 6F | |
| .byte $30 ; 70 kp 0 | |
| .byte $2E ; 71 kp . | |
| .byte $32 ; 72 kp 2 | |
| .byte $35 ; 73 kp 5 | |
| .byte $36 ; 74 kp 6 | |
| .byte $38 ; 75 kp 8 | |
| .byte $1B ; 76 esc | |
| .byte $00 ; 77 num lock | |
| .byte $8B ; 78 F11 | |
| .byte $2B ; 79 kp + | |
| .byte $33 ; 7A kp 3 | |
| .byte $2D ; 7B kp - | |
| .byte $2A ; 7C kp * | |
| .byte $39 ; 7D kp 9 | |
| .byte $8D ; 7E scroll lock | |
| .byte $00 ; 7F | |
| ; | |
| ; Table for shifted scancodes | |
| ; | |
| .byte $00 ; 80 | |
| .byte $C9 ; 81 F9 | |
| .byte $C7 ; 82 relocated F7 | |
| .byte $C5 ; 83 F5 (F7 actual scancode=83) | |
| .byte $C3 ; 84 F3 | |
| .byte $C1 ; 85 F1 | |
| .byte $C2 ; 86 F2 | |
| .byte $CC ; 87 F12 | |
| .byte $00 ; 88 | |
| .byte $CA ; 89 F10 | |
| .byte $C8 ; 8A F8 | |
| .byte $C6 ; 8B F6 | |
| .byte $C4 ; 8C F4 | |
| .byte $09 ; 8D tab | |
| .byte $7E ; 8E `~ | |
| .byte $CF ; 8F relocated Print Screen key | |
| .byte $03 ; 90 relocated Pause/Break key | |
| .byte $A0 ; 91 left alt (right alt) | |
| .byte $00 ; 92 left shift | |
| .byte $E0 ; 93 relocated Alt release code | |
| .byte $00 ; 94 left ctrl (and right ctrl) | |
| .byte $51 ; 95 qQ | |
| .byte $21 ; 96 1! | |
| .byte $00 ; 97 | |
| .byte $00 ; 98 | |
| .byte $00 ; 99 | |
| .byte $5A ; 9A zZ | |
| .byte $53 ; 9B sS | |
| .byte $41 ; 9C aA | |
| .byte $57 ; 9D wW | |
| .byte $40 ; 9E 2@ | |
| .byte $E1 ; 9F Windows 98 menu key (left side) | |
| .byte $02 ; A0 relocated ctrl-break key | |
| .byte $43 ; A1 cC | |
| .byte $58 ; A2 xX | |
| .byte $44 ; A3 dD | |
| .byte $45 ; A4 eE | |
| .byte $24 ; A5 4$ | |
| .byte $23 ; A6 3# | |
| .byte $E2 ; A7 Windows 98 menu key (right side) | |
| .byte $00 ; A8 | |
| .byte $20 ; A9 space | |
| .byte $56 ; AA vV | |
| .byte $46 ; AB fF | |
| .byte $54 ; AC tT | |
| .byte $52 ; AD rR | |
| .byte $25 ; AE 5% | |
| .byte $E3 ; AF Windows 98 option key (right click, right side) | |
| .byte $00 ; B0 | |
| .byte $4E ; B1 nN | |
| .byte $42 ; B2 bB | |
| .byte $48 ; B3 hH | |
| .byte $47 ; B4 gG | |
| .byte $59 ; B5 yY | |
| .byte $5E ; B6 6^ | |
| .byte $00 ; B7 | |
| .byte $00 ; B8 | |
| .byte $00 ; B9 | |
| .byte $4D ; BA mM | |
| .byte $4A ; BB jJ | |
| .byte $55 ; BC uU | |
| .byte $26 ; BD 7& | |
| .byte $2A ; BE 8* | |
| .byte $00 ; BF | |
| .byte $00 ; C0 | |
| .byte $3C ; C1 ,< | |
| .byte $4B ; C2 kK | |
| .byte $49 ; C3 iI | |
| .byte $4F ; C4 oO | |
| .byte $29 ; C5 0) | |
| .byte $28 ; C6 9( | |
| .byte $00 ; C7 | |
| .byte $00 ; C8 | |
| .byte $3E ; C9 .> | |
| .byte $3F ; CA /? | |
| .byte $4C ; CB lL | |
| .byte $3A ; CC ;: | |
| .byte $50 ; CD pP | |
| .byte $5F ; CE -_ | |
| .byte $00 ; CF | |
| .byte $00 ; D0 | |
| .byte $00 ; D1 | |
| .byte $22 ; D2 '" | |
| .byte $00 ; D3 | |
| .byte $7B ; D4 [{ | |
| .byte $2B ; D5 =+ | |
| .byte $00 ; D6 | |
| .byte $00 ; D7 | |
| .byte $00 ; D8 caps | |
| .byte $00 ; D9 r shift | |
| .byte $0D ; DA <Enter> | |
| .byte $7D ; DB ]} | |
| .byte $00 ; DC | |
| .byte $7C ; DD \| | |
| .byte $00 ; DE | |
| .byte $00 ; DF | |
| .byte $00 ; E0 | |
| .byte $00 ; E1 | |
| .byte $00 ; E2 | |
| .byte $00 ; E3 | |
| .byte $00 ; E4 | |
| .byte $00 ; E5 | |
| .byte $08 ; E6 bkspace | |
| .byte $00 ; E7 | |
| .byte $00 ; E8 | |
| .byte $91 ; E9 kp 1 | |
| .byte $2f ; EA kp / converted from E04A in code | |
| .byte $94 ; EB kp 4 | |
| .byte $97 ; EC kp 7 | |
| .byte $00 ; ED | |
| .byte $00 ; EE | |
| .byte $00 ; EF | |
| .byte $90 ; F0 kp 0 | |
| .byte $7F ; F1 kp . | |
| .byte $92 ; F2 kp 2 | |
| .byte $95 ; F3 kp 5 | |
| .byte $96 ; F4 kp 6 | |
| .byte $98 ; F5 kp 8 | |
| .byte $1B ; F6 esc | |
| .byte $00 ; F7 num lock | |
| .byte $CB ; F8 F11 | |
| .byte $2B ; F9 kp + | |
| .byte $93 ; FA kp 3 | |
| .byte $2D ; FB kp - | |
| .byte $2A ; FC kp * | |
| .byte $99 ; FD kp 9 | |
| .byte $CD ; FE scroll lock |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
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| ; Copyright 2020 Jonathan Foucher | |
| ; Permission is hereby granted, free of charge, to any person obtaining a copy of this software | |
| ; and associated documentation files (the "Software"), to deal in the Software without restriction, | |
| ; including without limitation the rights to use, copy, modify, merge, publish, distribute, | |
| ; sublicense, and/or sell copies of the Software, and to permit persons to whom the Software | |
| ; is furnished to do so, subject to the following conditions: | |
| ; The above copyright notice and this permission notice shall be included in all copies or | |
| ; substantial portions of the Software. | |
| ; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, | |
| ; INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR | |
| ; PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE | |
| ; FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR | |
| ; OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER | |
| ; DEALINGS IN THE SOFTWARE. | |
| ps2_irq: | |
| pha | |
| phx | |
| lda to_send | |
| bne @sending | |
| lda KB_STATE ; which state ? | |
| cmp #KB_STATE_START | |
| beq @start ; start bit | |
| cmp #KB_STATE_DATA ; get data bits | |
| beq @data | |
| cmp #KB_STATE_PARITY ; this is the parity bit | |
| beq @parity | |
| cmp #KB_STATE_STOP ; stop bit | |
| beq @stop | |
| jmp @exit | |
| @start: | |
| lda #KB_STATE_DATA | |
| sta KB_STATE ; next state will be to get data | |
| lda #0 | |
| sta KB_TEMP | |
| sta KB_BIT | |
| bra @exit | |
| @data: | |
| lda PORTB ; get the bit of data from PORTB bit 7 | |
| and #$80 | |
| ora KB_TEMP ; OR it with existing temp data | |
| sta KB_TEMP ; save it | |
| inc KB_BIT ; prepare for next bit | |
| lda KB_BIT | |
| cmp #8 ; if this is the last bit, next state is parity | |
| beq @next_state_parity | |
| lsr KB_TEMP ; if not last bit, shift KB_TEMP right to prepare for next bit | |
| bra @exit | |
| @next_state_parity: | |
| lda #KB_STATE_PARITY ;next state is parity | |
| sta KB_STATE | |
| bra @exit | |
| @parity: | |
| lda #KB_STATE_STOP ;next state is stop | |
| sta KB_STATE | |
| bra @exit | |
| @stop: | |
| lda #KB_STATE_START | |
| sta KB_STATE | |
| lda ignore_next | |
| bne @ignored | |
| ; Save key to character buffer | |
| ldx KB_TEMP | |
| cpx #$AA | |
| beq @init | |
| cpx #$FA | |
| beq @init | |
| cpx #$F0 | |
| beq @ignore_next | |
| ;stx PORTA | |
| lda ASCIITBL, x | |
| ldx KB_BUF_INDEX | |
| sta KB_BUF, x | |
| ;sta PORTA | |
| inc KB_BUF_INDEX | |
| @exit: | |
| plx | |
| pla | |
| rts | |
| @init: | |
| stx ready | |
| bra @exit | |
| @ignore_next: | |
| lda #1 | |
| sta ignore_next | |
| bra @exit | |
| @ignored: | |
| lda #0 | |
| sta ignore_next | |
| bra @exit | |
| @sending: | |
| ; lda #1 | |
| ; sta PORTA | |
| ; data pin of DDRB should be set as output by prepare_send | |
| lda KB_STATE ; which state ? | |
| cmp #KB_STATE_DATA ; send data bits | |
| beq @sending_data | |
| cmp #KB_STATE_PARITY ; this is the parity bit | |
| beq @sending_parity | |
| cmp #KB_STATE_STOP ; stop bit | |
| beq @sending_stop | |
| bra @exit | |
| @sending_data: | |
| ; lda #4 | |
| ; sta PORTA | |
| lda to_send ; get the bit of data from memory | |
| and #$01 ; get only bottom bit | |
| beq @send_zero | |
| @send_one: | |
| lda PORTB | |
| ora #$80 | |
| sta PORTB | |
| inc KB_PARITY | |
| bra @sending_done | |
| @send_zero: | |
| lda PORTB | |
| and #$7F | |
| sta PORTB | |
| @sending_done: | |
| ; lda #2 | |
| ; sta PORTA | |
| inc KB_BIT ; prepare for next bit | |
| lda KB_BIT | |
| cmp #8 ; if this is the last bit, next state is parity | |
| jmp @next_state_parity | |
| lsr to_send | |
| clc | |
| bra @exit | |
| @sending_parity: | |
| ; lda #5 | |
| ; sta PORTA | |
| lda KB_PARITY | |
| and #$01 | |
| beq @odd_parity ; send zero if odd parity | |
| lda PORTB | |
| ora #$80 ; send one if even | |
| sta PORTB | |
| lda #KB_STATE_STOP ;next state is stop | |
| sta KB_STATE | |
| bra @exit | |
| @odd_parity: | |
| lda PORTB | |
| and #$7F | |
| sta PORTB | |
| lda #KB_STATE_STOP ;next state is stop | |
| sta KB_STATE | |
| bra @exit | |
| @sending_stop: | |
| ; lda #6 | |
| ; sta PORTA | |
| lda #KB_STATE_START ; set it back to start in case we are receivin next | |
| sta KB_STATE | |
| lda #0 | |
| sta to_send | |
| sta KB_BIT | |
| sta KB_PARITY | |
| lda DDRB ; set PORTB back to input | |
| and #$7F | |
| sta DDRB | |
| jmp @exit |
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