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138 lines
4.2 KiB
NASM
138 lines
4.2 KiB
NASM
; kbd - implement GetC for PS/2 keyboard
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;
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; It reads raw key codes from a FetchKC routine and returns, if appropriate,
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; a proper ASCII char to type. See recipes rc2014/ps2 and sms/kbd.
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;
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; *** Defines ***
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; Pointer to a routine that fetches the last typed keyword in A. Should return
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; 0 when nothing was typed.
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; KBD_FETCHKC
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; *** Consts ***
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.equ KBD_KC_BREAK 0xf0
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.equ KBD_KC_EXT 0xe0
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.equ KBD_KC_LSHIFT 0x12
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.equ KBD_KC_RSHIFT 0x59
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; *** Variables ***
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; Set to previously received scan code
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.equ KBD_PREV_KC KBD_RAMSTART
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; Whether Shift key is pressed. When not pressed, holds 0. When pressed, holds
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; 0x80. This allows for quick shifting in the glyph table.
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.equ KBD_SHIFT_ON @+1
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.equ KBD_RAMEND @+1
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kbdInit:
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xor a
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ld (KBD_PREV_KC), a
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ld (KBD_SHIFT_ON), a
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ret
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kbdGetC:
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call KBD_FETCHKC
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or a
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jr z, .nothing
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; scan code not zero, maybe we have something.
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; Do we need to skip it?
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ex af, af' ; save fetched KC
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ld a, (KBD_PREV_KC)
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; Whatever the KC, the new A becomes our prev. The easiest way to do
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; this is to do it now.
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ex af, af' ; restore KC
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ld (KBD_PREV_KC), a
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ex af, af' ; restore prev KC
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; If F0 (break code) or E0 (extended code), we skip this code
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cp KBD_KC_BREAK
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jr z, .break
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cp KBD_KC_EXT
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jr z, .nothing
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ex af, af' ; restore saved KC
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; A scan code over 0x80 is out of bounds or prev KC tell us we should
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; skip. Ignore.
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cp 0x80
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jr nc, .nothing
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; No need to skip, code within bounds, we have something!
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call .isShift
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jr z, .shiftPressed
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; Let's see if there's a ASCII code associated to it.
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push hl ; --> lvl 1
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ld hl, KBD_SHIFT_ON
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or (hl) ; if shift is on, A now ranges in 0x80-0xff.
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ld hl, kbdScanCodes ; no flag changed
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call addHL
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ld a, (hl)
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pop hl ; <-- lvl 1
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or a
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jr z, kbdGetC ; no code.
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; We have something!
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cp a ; ensure Z
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ret
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.shiftPressed:
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ld a, 0x80
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ld (KBD_SHIFT_ON), a
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jr .nothing ; no actual char to return
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.break:
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ex af, af' ; restore saved KC
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call .isShift
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jr nz, .nothing
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; We had a shift break, update status
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xor a
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ld (KBD_SHIFT_ON), a
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; continue to .nothing
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.nothing:
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; We have nothing. Before we go further, we'll wait a bit to give our
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; device the time to "breathe". When we're in a "nothing" loop, the z80
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; hammers the device really fast and continuously generates interrupts
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; on it and it interferes with its other task of reading the keyboard.
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xor a
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.wait:
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inc a
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jr nz, .wait
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jr kbdGetC
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; Whether KC in A is L or R shift
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.isShift:
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cp KBD_KC_LSHIFT
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ret z
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cp KBD_KC_RSHIFT
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ret
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; A list of the values associated with the 0x80 possible scan codes of the set
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; 2 of the PS/2 keyboard specs. 0 means no value. That value is a character that
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; can be read in a GetC routine. No make code in the PS/2 set 2 reaches 0x80.
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kbdScanCodes:
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; 0x00 1 2 3 4 5 6 7 8 9 a b c d e f
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.db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9,'`', 0
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; 0x10 9 = TAB
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.db 0, 0, 0, 0, 0,'q','1', 0, 0, 0,'z','s','a','w','2', 0
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; 0x20 32 = SPACE
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.db 0,'c','x','d','e','4','3', 0, 0, 32,'v','f','t','r','5', 0
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; 0x30
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.db 0,'n','b','h','g','y','6', 0, 0, 0,'m','j','u','7','8', 0
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; 0x40 59 = ;
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.db 0,',','k','i','o','0','9', 0, 0,'.','/','l', 59,'p','-', 0
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; 0x50 13 = RETURN 39 = '
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.db 0, 0, 39, 0,'[','=', 0, 0, 0, 0, 13,']', 0,'\', 0, 0
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; 0x60 8 = BKSP
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.db 0, 0, 0, 0, 0, 0, 8, 0, 0,'1', 0,'4','7', 0, 0, 0
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; 0x70 27 = ESC
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.db '0','.','2','5','6','8', 27, 0, 0, 0,'3', 0, 0,'9', 0, 0
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; Same values, but shifted, exactly 0x80 bytes after kbdScanCodes
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; 0x00 1 2 3 4 5 6 7 8 9 a b c d e f
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.db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9,'~', 0
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; 0x10 9 = TAB
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.db 0, 0, 0, 0, 0,'Q','!', 0, 0, 0,'Z','S','A','W','@', 0
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; 0x20 32 = SPACE
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.db 0,'C','X','D','E','$','#', 0, 0, 32,'V','F','T','R','%', 0
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; 0x30
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.db 0,'N','B','H','G','Y','^', 0, 0, 0,'M','J','U','&','*', 0
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; 0x40 59 = ;
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.db 0,'<','K','I','O',')','(', 0, 0,'>','?','L',':','P','_', 0
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; 0x50 13 = RETURN
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.db 0, 0,'"', 0,'{','+', 0, 0, 0, 0, 13,'}', 0,'|', 0, 0
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; 0x60 8 = BKSP
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.db 0, 0, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 0, 0, 0
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; 0x70 27 = ESC
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.db 0, 0, 0, 0, 0, 0, 27, 0, 0, 0, 0, 0, 0, 0, 0, 0
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