Applecorn/auxmem.chario.s

731 lines
27 KiB
ArmAsm

* AUXMEM.CHARIO.S
* (c) Bobbi 2021,2022 GPLv3
*
* AppleMOS Character I/O
* KERNEL/CHARIO.S
*****************
* Character read and write
*
* 14-Aug-2021 Flashing cursor and INKEY sync'd to frame rate
* with VBLK. Ensured cursor turned on straight away.
* 15-Aug-2021 Cursor keys move copy cursor, copy reads char.
* Copy cursor not visible yet.
* 16-Aug-2021 Copy cursor and Edit cursor visible.
* 17-Aug-2021 OSBYTE 4 for cursors, OSBYTE 221-228 for topbit
* keys.
* 21-Aug-2021 FIXED: If screen scrolls, copy cursor ends on
* wrong line.
* FIXED: KBDREAD has several paths that don't
* test ESCHAR.
* FIXED: INKEY doesn't restore cursor on timeout.
* The three separate cursors can be set seperately.
* 02-Sep-2021 INKEY-256 tests Apple IIe vs IIc.
* 05-Sep-2021 KBDINIT returns startup value to pass to VDUINT.
* 09-Sep-2021 Moved keyboard OSBYTEs to here.
* 12-Sep-2021 COPY calls new VDU entry point.
* 15-Sep-2021 INKEY(0) tests once and returns immediately.
* 30-Nov-2021 With *FX4,<>0 TAB returns $09, allows eg VIEW to work.
* 15-Oct-2022 Replace calling KBDCHKESC with ESCPOLL, does translations, etc.
* Fixed bug with cursor keys after *FX4,2. OSRDCH enables IRQs.
* 23-Oct-2022 Escape: BYTE7E needed to ESCPOLL, INKEYESC unbalanced stack.
* 03-Nov-2022 Escape: Fixed INKEY loop failing if entering with previous Escape,
* combined with EscAck clearing keyboard.
* 06-Dec-2022 Moved *KEY into here.
* 12-Dec-2022 Test code to write *KEY data to mainmem.
* Hardware locations
KBDDATA EQU $C000 ; Read Keyboard data
KBDACK EQU $C010 ; Acknowledge keyboard data
KBDAPPLFT EQU $C061 ; Left Apple key
KBDAPPRGT EQU $C062 ; Right Apple key
IOVBLNK EQU $C019 ; VBLNK pulse
FLASHER EQU BYTEVARBASE+176 ; VSync counter for flashing cursor
FXEXEC EQU BYTEVARBASE+198
FXSPOOL EQU BYTEVARBASE+199
FXTABCHAR EQU BYTEVARBASE+219
FXESCCHAR EQU BYTEVARBASE+220
FXKEYBASE EQU BYTEVARBASE+221
FXESCON EQU BYTEVARBASE+229
FXESCEFFECT EQU BYTEVARBASE+230
FX200VAR EQU BYTEVARBASE+200
FXSOFTLEN EQU BYTEVARBASE+216
FXSOFTOK EQU BYTEVARBASE+244
FX254VAR EQU BYTEVARBASE+254
FX2VAR EQU BYTEVARBASE+$B1
FX3VAR EQU BYTEVARBASE+$EC
FX4VAR EQU BYTEVARBASE+$ED
* OSWRCH handler
****************
* Send a character to current output
* All registers preserved
*
WRCHHND PHA
PHX
PHY
PHA
* TO DO Check any output redirections
* TO DO Check any printer output
JSR OUTCHAR ; Send to VDU driver
* BCC WRCHHND3 ; VDU driver says skip printer
* PLA ; Get character back
* PHA
* JSR PRNCHAR ; Send to printer
* WRCHHND3
* Check FX3VAR
* Bxx WRCHHND4 ; Spool disabled
LDY FXSPOOL ; See if *SPOOL is in effect
BEQ WRCHHND4 ; No, skip sending to spool file
PLA
PHA
JSR OSBPUT ; Write character to spool file
WRCHHND4 PLA ; Drop stacked character
PLY ; Restore everything
PLX
PLA
RTS
* Character Input
*****************
* Default keyboard OSBYTE variables
DEFBYTELOW EQU 219 ; First default OSBYTE value
DEFBYTE DB $09,$1B ; Default key codes
DB $01,$D0,$E0,$F0 ; Default key expansion
DB $01,$80,$90,$00 ; Default key expansion
DEFBYTEEND
KBDINIT LDX #DEFBYTEEND-DEFBYTE-1
:KBDINITLP LDA DEFBYTE,X ; Initialise KBD OSBYTE variables
STA BYTEVARBASE+DEFBYTELOW,X
DEX
BPL :KBDINITLP
JSR SOFTKEYCHK ; Clear soft keys
LDX #$C3
STX FX254VAR ; b7-b4=default KBD map, b3-b0=default MODE
BIT SETV ; Set V
JSR KBDTEST ; Test if key being pressed
BCS :KBDINITOK ; Return default MODE=3
STA KBDACK ; Ack. keypress
TAX ; Use keypress as default MODE
:KBDINITOK TXA
RTS
* OSRDCH/INKEY handler
**********************
* Read a character from current input
* All registers preserved except A, Carry
* Flashes a soft cursor while waiting for input
* *NB* OSRDCH returns with IRQs enabled, INKEY returns with IRQs preserved
*
RDCHHND LDA #$80 ; flag=wait forever
PHY
TAY
BRA INKEYGO ; Wait forever for input
* XY<$8000 - wait for a keypress
INKEY PHY ; Dummy PHY to balance RDCH
INKEYGO CLI ; Enable IRQs
PHX ; Save registers
PHY
BIT VDUSTATUS ; Enable editing cursor
BVC INKEYGO2 ; No editing cursor
JSR GETCHRC ; Get character under cursor
STA COPYCHAR ; Save char under edit cursor
LDA CURSORED
JSR PUTCHRC ; Display edit cursor
JSR COPYSWAP1 ; Swap to copy cursor
INKEYGO2 JSR GETCHRC ; Get character under cursor
STA OLDCHAR
BRA INKEY1 ; Turn cursor on
INKEYLP CLC
LDA #$01 ; Slow flash, every 32 frames
BIT VDUSTATUS
BVC INKEY0
ASL A ; Fast flash, every 16 frames
INKEY0 ADC FLASHER
STA FLASHER
AND #15
BNE INKEY3 ; Not time to toggle yet
LDA OLDCHAR ; Prepare to remove cursor
BIT FLASHER
BMI INKEY2 ; Remove cursor
INKEY1 LDA CURSOR ; Add cursor
BIT VDUSTATUS
BVC INKEY2
LDA CURSORCP
INKEY2 JSR PUTCHRC ; Toggle cursor
INKEY3 LDA #$27 ; Prepare to return CHR$27 if Escape state
CLC
BIT ESCFLAG ; Check Escape state
BMI INKEYESC ; Escape pending, return it with A=27
INKEY4 JSR KEYREAD ; Test for input, all can be trashed
PLY
BCC INKEYOK ; Char returned, return it
BMI INKEY6 ; Loop forever, skip countdown
PLX
BNE INKEY5
TYA
BEQ INKEYOUT ; XY=0, timed out
DEY ; 16-bit decrement
INKEY5 DEX
PHX
INKEY6 PHY
*
* VBLK pulses at 50Hz/60Hz, toggles at 100Hz/120Hz
LDX IOVBLNK ; Get initial VBLK state
INKEY8 BIT KBDDATA
BMI INKEY4 ; Key pressed
TXA
EOR IOVBLNK
BPL INKEY8 ; Wait for VBLK change
BMI INKEYLP ; Loop back to key test
INKEYOUT LDA #$FF ; Prepare to stack $FF
INKEYESC PLY ; Drop stacked Y
INKEYOK PHA ; Save key or timeout
PHP ; Save CC=key, CS=timeout
LDA OLDCHAR ; Prepare for main cursor
BIT VDUSTATUS
BVC INKEYOFF2 ; No editing cursor
JSR PUTCHRC ; Remove cursor
JSR COPYSWAP1 ; Swap cursor back
LDA COPYCHAR ; Remove main cursor
INKEYOFF2 JSR PUTCHRC ; Remove cursor
PLP
BCS INKEYOK3 ; Timeout
LDA ESCFLAG ; Keypress, test for Escape
ASL A ; Cy=Escape flag
PLA ; Get char back
PLX ; Restore X,Y for key pressed
INKEYOK3 PLY ; Or pop TimeOut
RTS
* RDCH Character read: CC, A=char, X=restored, Y=restored
* RDCH Escape: CS, A=char, X=restored, Y=restored
* INKEY Character read: CC, A=char, X=???, Y<$80
* INKEY Escape: CS, A=char, X=???, Y<$80
* INKEY Timeout: CS, A=???, X=???, Y=$FF
BYTE81 TYA
BMI NEGINKEY ; XY<0, scan for keypress
JSR INKEY ; XY>=0, wait for keypress
* Character read: CC, A=char, X=???, Y<$80
* Escape: CS, A=char, X=???, Y<$80
* Timeout: CS, A=???, X=???, Y=$FF
TAX ; X=character returned
TYA
BMI BYTE81DONE ; Y=$FF, timeout
LDY #$00
BCC BYTE81DONE ; CC, not Escape
LDY #$1B ; Y=27
BYTE81DONE RTS
* Returns: Y=$FF, X=???, CS - timeout
* Y=$1B, X=???, CS - escape
* Y=$00, X=char, CC - keypress
NEGINKEY CPX #$01
LDX #$00 ; Unimplemented
BCS NEGINKEY0
JSR NEGCALL ; Read machine ID from mainmem
LDX #$2C
TAY
BEQ NEGINKEY0 ; $00 = Apple IIc -> INKEY-256 = $2C
LDX #$2E
AND #$0F
BEQ NEGINKEY0 ; $x0 = Apple IIe -> INKEY-256 = $2E
LDX #$2A ; else = Apple IIgs -> INKEY-256 = $2A
NEGINKEY0 LDY #$00
NEGINKEY1 CLC
RTS
NEGCALL >>> XF2MAIN,MACHRD ; Try to read Machine ID
* KERNEL/KEYBOARD.S
*******************
* SOFT KEY PROCESSING
* ===================
* *KEY <num> <GSTRANS string>
* ---------------------------
STARKEY LDA FXSOFTLEN
BNE ERRKEYUSED ; Key being expanded
JSR SCANDEC
CMP #$10
BCC STARKEY1
ERRBADKEY BRK
DB $FB
ASC 'Bad key'
ERRKEYUSED BRK
DB $FA
ASC 'Key in use'
BRK
*
* A slightly fiddly procedure, as we need to check the new
* definition is valid before we insert it, we can't bomb
* out halfway through inserting a string, and we mustn't
* have mainmem paged in while parsing the string as the
* string might be "underneath" the memory we've paged in,
* we don't know how long the new definition is and if
* it will fit into memory until after we've parsed it, so
* we either have to store it to a temp area or parse it
* twice.
*
* All this, and we need a structure that is reasonably coded,
* but with the priority to be easy for KEYREAD to extract
* from (as called more often), even if at expense of storing
* being more complex.
*
* Optimisations:
* BBC doesn't care if the new definition is valid, it removes
* the current definition before parsing, so a parse error
* results in the definition being cleared.
* eg *KEY 1 HELLO, *KEY 1 X gives Bad string and key 1=""
*
* BBC uses (simplified):
* SOFTBUF+key+0 -> start of definition
* SOFTBUF+key+1 -> after last byte of definition
* SOFTBUF+16 -> free space after end of last definition
* definitions stored in order of creation
*
* Master uses:
* SOFTBUF+key -> lo.start of definition
* SOFTBUF+key+17 -> hi.start of definition
* SOFTBUF+key+1 -> lo.after last byte definition
* SOFTBUF+key+18 -> hi.after last byte definition
* SOFTBUF+16/33 -> free space after last byte last definition
* definitions stored in key order
*
* Initial development layout:
* 00..0F -> length of string 0..15
* 10... -> strings in key order
* (len0+len1+...len15) => start of free space
*
STARKEY1 STA FKEYNUM ; Key number being defined
JSR KEYOPENGAP
JSR SKIPCOMMA
SEC
JSR GSINIT ; Initialise '*KEY-type string'
LDX KEYINS ; Starting point to insert
STARKEYLP1 JSR GSREAD
BCS STARKEYEND
>>> WRTMAIN ; Write main memory
STA FKEYBUF,X ; Store char of definition
>>> WRTAUX ; Back to writing aux again
INX
CPX MOVEDST ; See if we are out of space
BNE STARKEYLP1
LDX FKEYNUM
>>> WRTMAIN ; Write main memory
STZ FKEYLENS,X ; Out of space. Set len=0
>>> WRTAUX ; Back to writing aux again
BRA STARKEYCLS
STARKEYEND TXA ; Last idx+1
SEC ; Compute length
SBC KEYINS
LDX FKEYNUM
>>> WRTMAIN ; Write main memory
STA FKEYLENS,X ; Store length of new def
>>> WRTAUX ; Back to writing aux again
STARKEYCLS JSR KEYCLSGAP
RTS
FKEYNUM DB $00
KEYINS DB $00
* Open gap in FKEYBUF to allow new def to be inserted
* Moved defs for keys FKEYNUM+1..15 to top of FKEYBUF
* Preserves A,X,Y
KEYOPENGAP PHA
PHX
PHY
LDX FKEYNUM ; Key being defined
JSR KEYSUMLENS ; Len of defs 0..X exclusive
STA KEYINS ; Offset for insert
LDX FKEYNUM ; Key being defined
INX
JSR KEYSUMLENS ; Len of defs 0..X exclusive
STA MOVESRC ; Source offset for move
LDX #16 ; Sum keys 0..15 (ie: all)
JSR KEYSUMLENS ; Sum them all
SEC
SBC MOVESRC ; Compute length to move
STA MOVELEN
LDA #$FF ; Length of FKEYBUF
SEC
SBC MOVELEN ; Compute dest for move
STA MOVEDST ; Dest offset for move
JSR MOVEKEYS ; Open the gap
PLY
PLX
PLA
RTS
* After the gap is opened, there is freespace from MOVESRC to MOVEDST-1
* Close gap in FKEYBUF after def has been inserted
* Preserves A,X,Y
KEYCLSGAP PHA
PHX
PHY
LDA #$FF ; Length of FKEYBUF
SEC
SBC MOVEDST ; Previous dest, to calc length
STA MOVELEN ; Length for move
LDA MOVEDST ; Old dest ...
STA MOVESRC ; ... is new source
LDX FKEYNUM ; Key being defined
INX
JSR KEYSUMLENS ; Len of defs 0..X exclusive
STA MOVEDST ; New dest
JSR MOVEKEYS ; Close the gap
PLY
PLX
PLA
RTS
* Add lengths of *KEY definitions together
* On entry: X is the highest key num + 1 (sums 0..X-1)
* On return: Sum in A (exclusive of X)
* From *KEY0 to *KEYn where n is value in X
KEYSUMLENS LDA #$00 ; Clear sum
:LOOP CPX #$00
BEQ :DONE
>>> RDMAIN ; Read main memory
CLC
ADC FKEYLENS-1,X ; Add lengths
>>> RDAUX ; Read aux memory
DEX
BRA :LOOP
:DONE RTS
* Move key definitions within FKEYBUF
* Copies MOVELEN bytes from MOVSRC->MOVDST within FKEYBUF
MOVEKEYS LDX MOVESRC
LDY MOVEDST
:L1 LDA MOVELEN
BEQ :DONE
>>> RDMAIN ; Read main memory
LDA FKEYBUF,X
>>> RDAUX ; Read aux memory
>>> WRTMAIN ; Write main memory
STA FKEYBUF,Y
>>> WRTAUX ; Write aux memory
INX
INY
DEC MOVELEN
BRA :L1
:DONE RTS
MOVESRC DB $00 ; Source offset in FKEYBUF
MOVEDST DB $00 ; Dest offset in FKEYBUF
MOVELEN DB $00 ; # bytes remaining to move
* OSBYTE &12 - Clear soft keys
* ----------------------------
SOFTKEYCHK LDA FXSOFTOK
BEQ BYTE12OK ; Soft keys ok, exit
BYTE12 LDX #$FF
STX FXSOFTOK ; Soft keys being updated
:L1 >>> WRTMAIN ; Zero the buffer (nice when debugging)
STZ FKEYBUF,X
>>> WRTAUX
DEX
BNE :L1
LDX #15
:L2 >>> WRTMAIN ; Zero the lengths
STZ FKEYLENS,X
>>> WRTAUX
DEX
BNE :L2
STZ FXSOFTOK ; Soft keys updated
BYTE12OK RTS
* Handle function keys on ADB Extended Keyboard & BMOW Wombat
* For Apple IIGS only
EXTENDKBD BIT VDUBANK ; Use VDUBANK to see if ...
BMI :GS ; ... this is a GS
RTS ; If not, bail
:GS PHA ; Preserve character typed
LDA KEYMOD ; GS-specific register
AND #$10 ; Bit 4 is the 'keypad bit'
BEQ :NOTKEYPAD ; Not an extended key
PLA
LDX #$00
:LOOP CMP :TABLE,X ; Lookup keycode in table
BEQ :FOUND
INX
INX
CPX #20 ; 10 rows of two bytes each
BNE :LOOP
RTS ; Not found, return unchanged
:FOUND LDA KEYMOD ; Look at the modifiers
AND #$C3 ; Mask only the modifier bits
CMP #$01 ; Only shift pressed
BNE :S1
LDA #$10 ; Offset for shift+f-key
BRA :S2
:S1 CMP #$02 ; Onlt ctrl pressed
BNE :S2
LDA #$20 ; Offset for ctrl+f-key
:S2 CLC
ADC :TABLE+1,X ; Lookup translation + add
RTS
* TODO Add $10 if shift is down
* TODO Add $20 if ctrl is down
RTS
:NOTKEYPAD PLA ; Get original key back
RTS
:TABLE DB $7A, $81 ; Extended keyboard F1 code -> f1
DB $78, $82 ; Extended keyboard F2 code -> f2
DB $63, $83 ; Extended keyboard F3 code -> f3
DB $76, $84 ; Extended keyboard F4 code -> f4
DB $60, $85 ; Extended keyboard F5 code -> f5
DB $61, $86 ; Extended keyboard F6 code -> f6
DB $62, $87 ; Extended keyboard F7 code -> f7
DB $64, $88 ; Extended keyboard F8 code -> f8
DB $65, $89 ; Extended keyboard F9 code -> f9
DB $6D, $80 ; Extended keyboard F10 code -> f0
* KEYREAD
************************
* Test for and read from input,
* expanding keyboard special keys
*
* On exit, CS=no keypress
* CC=keypress
* A =keycode, X,Y=corrupted
KEYREAD LDY FXEXEC ; See if EXEC file is open
BEQ KEYREAD1 ; No, skip past
JSR OSBGET ; Read character from file
BCC KEYREADOK ; Not EOF, return it
LDA #$00 ; EOF, close EXEC file
STA FXEXEC ; Clear EXEC handle
JSR OSFIND ; And close it
KEYREAD1 LDA FXSOFTLEN ; Are we replaying a function key?
BEQ KEYREAD2 ; No, skip over
LDX SOFTKEYOFF ; Obtain current f-key buffer offset
>>> RDMAIN
LDA FKEYBUF,X ; Read char from buf in main mem
>>> RDAUX
INC SOFTKEYOFF ; Next char in buffer
DEC FXSOFTLEN ; One less char remaining
CLC
RTS
KEYREAD2 JSR KBDREAD ; Fetch character from KBD "buffer"
BCS KEYREADOK ; Nothing pending
JSR EXTENDKBD ; Handle ADB Extended Keyboard f-keys
TAY ; Y=unmodified character
BPL KEYREADOK ; Not top-bit key
AND #$CF ; Drop Shift/Ctrl bits
CMP #$C9
BCC KEYSOFTY ; Not cursor key
LDX FX4VAR
BEQ KEYCURSOR ; *FX4,0 - editing keys
CPY #$C9
CLV
BEQ KEYCOPYTAB ; TAB key
DEX
BNE KEYSOFTHI ; Not *FX4,1 - soft key
SBC #$44 ; Return $88-$8B
KEYREADOK1 CLC
KEYREADOK RTS
* Process soft key
KEYSOFTHI LDX FX254VAR
CPX #$C0
BCC KEYSOFTY
TYA
AND #$BF
TAY
KEYSOFTY TYA ; Get key including Shift/Ctrl
LSR A
LSR A
LSR A
LSR A ; A=key DIV 16
EOR #$04 ; Offset into KEYBASE
TAX
LDA FXKEYBASE-8,X
BEQ KEYNONE ; Value 0 means 'ignore key'
DEC A
BEQ EXPANDKEY ; Value 1 means 'expand key'
TYA
AND #$0F
CLC
ADC FXKEYBASE-8,X
CLC
RTS
* Expand soft key
* On entry: Y key code ($8n where n is F-key num)
EXPANDKEY TYA
AND #$0F ; Obtain F-key number
TAX
PHX
JSR KEYSUMLENS ; Obtain starting offset
STA SOFTKEYOFF
PLX
>>> RDMAIN
LDA FKEYLENS,X ; Obtain length of *KEY string
>>> RDAUX
STA FXSOFTLEN
RTS
SOFTKEYOFF DB $00
* Process cursor keys
KEYCURSOR CMP #$C9
BEQ KEYCOPY
PHA
LDA OLDCHAR
JSR PUTCHRC ; Remove cursor
PLA
JSR COPYMOVE ; Move copy cursor
JSR GETCHRC ; Save char under cursor
STA OLDCHAR
KEYNONE SEC
RTS
KEYCOPY BIT VDUSTATUS
KEYCOPYTAB LDA FXTABCHAR ; Prepare TAB if no copy cursor
BVC KEYREADOK1 ; No copy cursor, return TAB
LDA OLDCHAR ; Get the char under cursor
PHA
JSR OUTCHARCP ; Output it to restore and move cursor
JSR GETCHRC ; Save char under cursor
STA OLDCHAR
PLA
BNE KEYREADOK1 ; Ok character
SEC
JMP BEEP ; Beep and return CS=No char
* KBDREAD
************************
* Test for and fetch key from keyboard
*
* On exit, CS=no keypress
* CC=keypress
* A =keycode, X=corrupted
* Apple+Letter -> Ctrl+Letter
* Apple+Digits -> 80+x, 90+x, A0+x
* TAB -> $C9
* Cursors -> $CC-$CF
*
KBDREAD CLV ; VC=return keypress
KBDTEST LDA KBDDATA ; VS here to test for keypress
EOR #$80 ; Toggle bit 7
CMP #$80
BCS KBDDONE ; No key pressed
BVS KBDDONE ; VS=test for keypress
STA KBDACK ; Ack. keypress
KBDREAD2 BIT KBDAPPLFT
BMI KBDLALT ; Left Apple pressed
BIT KBDAPPRGT
BMI KBDRALT ; Right Apple pressed
CMP #$09
BEQ KBDTAB ; TAB is dual action TAB/COPY
CMP #$08
BCC KBDCHKESC ; <$08 not cursor key
CMP #$0C
BCC KBDCURSR ; $08-$0B are cursor keys
CMP #$15
BNE KBDCHKESC ; $15 is cursor key
*
KBDCUR15 LDA #$0D ; Convert RGT to $09
KBDTAB SBC #$04 ; Convert TAB to &C9
KBDCURSR CLC
ADC #$C4 ; Cursor keys $C0+x
BRA KBDCHKESC
KBDRALT ; Right Apple key pressed
KBDLALT CMP #$40 ; Left Apple key pressed
BCS KBDCTRL
CMP #$30
BCC KBDCHKESC ; <'0'
CMP #$3A
BCS KBDCHKESC ; >'9'
KBDFUNC AND #$0F ; Convert Apple-Num to function key
ORA #$80
KBDFUNC2 BIT KBDAPPRGT
BPL KBDCHKESC ; Left+Digit -> $8x
ORA #$90 ; Right+Digit -> $9x
BIT KBDAPPLFT
BPL KBDCHKESC
EOR #$30 ; Left+Right+Digit -> $Ax
BRA KBDCHKESC
KBDCTRL AND #$1F ; Apple-Letter -> Ctrl-Letter
*
* Test for Escape character
KBDCHKESC TAX ; X=keycode
EOR FXESCCHAR ; Current ESCAPE char?
ORA FXESCON ; Is ESCAPE an ASCII char?
BNE KBDNOESC ; Not ESCAPE or ESCAPE=ASCII
LDA FX200VAR ; Is ESCAPE ignored?
LSR A ; Check bit 0
BCS KBDDONE ; ESCAPE completely ignored
SEC
ROR ESCFLAG ; Set Escape flag
KBDNOESC TXA ; A=keycode
CLC ; CLC=Ok
KBDDONE RTS
* Poll the keyboard to update Escape state
* On exit, MI=Escape state pending
* CC=key pressed, CS=no key pressed
* A=character
* X,Y=preserved
*
ESCPOLL BIT SETV ; Set V
JSR KBDTEST ; VS - test keyboard
BCS ESCPOLL9 ; No keypress pending
PHX ; KBDREAD corrupts A,X
JSR KBDREAD2 ; Read key and check for Escape, returns CC
PLX
ESCPOLL9 BIT ESCFLAG ; Return with Escape state
RTS
* Process pending Escape state
BYTE7E STA KBDACK ; Flush keyboard
LDX #$00 ; $7E = ack detection of ESC
BIT ESCFLAG
BPL BYTE7DOK ; No Escape pending
LDA FXESCEFFECT ; Process Escape effects
BEQ BYTE7E2
CLI ; Allow IRQs while flushing
STX FXLINES ; Clear scroll counter
STX FXSOFTLEN ; Cancel soft key expansion
JSR CMDEXEC0 ; Close any EXEC file
* JSR BUFFLUSHALL ; Flush all buffers (this should do FXSOFTLEN)
BYTE7E2 LDX #$FF ; X=$FF, Escape was pending
BYTE7C CLC ; &7C = clear escape condition
BYTE7D ROR ESCFLAG ; $7D = set escape condition
BYTE7DOK RTS
BYTE76 LDX #$00 ; Update LEDs and return X=SHIFT
RTS ; Not possible with Apple