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95 lines
2.5 KiB
NASM
95 lines
2.5 KiB
NASM
; kbd - implement GetC for PS/2 keyboard
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;
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; Status: Work in progress. See recipes/rc2014/ps2
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;
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; *** Defines ***
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; The port of the device where we read scan codes. See recipe rc2014/ps2.
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; KBD_PORT
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; *** Variables ***
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.equ KBD_SKIP_NEXT KBD_RAMSTART
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.equ KBD_RAMEND KBD_SKIP_NEXT+1
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kbdInit:
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xor a
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ld (KBD_SKIP_NEXT), a
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ret
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kbdGetC:
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in a, (KBD_PORT)
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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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push af ; <|
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ld a, (KBD_SKIP_NEXT) ;|
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or a ; |
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jr nz, .skip ; |
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pop af ; <|
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cp 0x80
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jr nc, .outOfBounds
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; No need to skip, code within bounds, we have something! Let's see if
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; there's a ASCII code associated to it.
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push hl ; <|
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ld hl, kbdScanCodes ; |
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call addHL ; |
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ld a, (hl) ; |
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pop hl ; <|
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or a
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jp z, unsetZ ; no code. Keep A at 0, but unset Z
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; We have something!
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cp a ; ensure Z
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ret
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.outOfBounds:
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; A scan code over 0x80 is out of bounds. Ignore.
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; If F0 (break code) or E0 (extended code), we also skip the next code
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cp 0xf0
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jr z, .skipNext
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cp 0xe0
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jr z, .skipNext
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xor a
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jp unsetZ
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.skipNext:
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ld (KBD_SKIP_NEXT), a
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xor a
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jp unsetZ
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.skip:
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pop af ; equilibrate stack
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xor a
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ld (KBD_SKIP_NEXT), a
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jp unsetZ
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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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push bc
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ld b, 0
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.wait:
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nop
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djnz .wait
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pop bc
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jp unsetZ
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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 than
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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, 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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