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tadjm.asm
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;TADJM.SAM
NMISTOP: LD SP,ISPVAL
LD DE,MAINER
PUSH DE
LD (ERRSP),SP
RST &08
DB 15 ;"BREAK into program"
;GET KEY FROM BUFFER (ACTUALLY, LASTK). NZ=GOT KEY IN A, ELSE A=0
GETKEY: CALL KEYRD
RET Z ;RET IF NO KEY - Z
JR KBF2
;USED BY INKEY$
READKEY: RST &30
DW TWOKSC
JR Z,RKY2 ;JR IF GOT CODES IN DE
XOR A
RET ;RET IF NO KEY - Z,NC
RKY2: RST &30
DW KYVL ;USE DE TO GET KEYMAP CODE IN A
AND A ;NZ
SCF ;"GOT KEY"
KBFLUSH: LD HL,0
LD (KBQP),HL ;EMPTY QUEUE
KBF2: LD HL,FLAGS
RES 5,(HL) ;"NO KEY"
RET
KEYRD: RST &30
DW KEYRD2
LD A,(FLAGS)
AND &20 ;Z IF NO KEY
LD A,(LASTK)
JR KBF2 ;SHOW "NO KEY" IN CASE WE GOT ONE
;FPSTACK.SAM - FPCS SUBROUTINES
;STACKA - STACK "A" REGISTER ON FPCS. EXIT WITH DE=STKEND
;STACKBC - DITTO WITH BC
;STACKHL - DITTO WITH HL
STACKHL: LD D,L
LD C,H
JR STACKCM
STACKA: LD B,0
LD C,A
STACKBC: LD D,C
LD C,B
STACKCM: XOR A ;NC
LD B,A
LD E,A
;ENTRY FROM TRUNC$
STKSTOREX: CALL STKSTORE
EX DE,HL ;DE=STKEND
RET
;STORE A STRING. DE=START, BC=LEN. PAGE IS ASSUMED TO BE SWITCHED IN
STKSTOREP: IN A,(251)
;STACK-STORE
STKST0: AND &7F ;BIT 7=0 IF ARRAY OR "SLICED". BITS 4-0=START PAGE
STKSTOS: LD HL,FLAGS
RES 6,(HL) ;STRING RESULT
STKSTORE: LD HL,(STKEND)
LD (HL),A ;PAGE AND FLAG IF STRING, EXPONENT IF FP NUMBER
INC HL
LD (HL),E ;E=SIGN IF SMALL INTEGER
INC HL
LD (HL),D ;START IF STRING
INC HL
LD (HL),C ;CD=INTEGER IF SMALL INTEGER
INC HL
LD (HL),B ;LEN IF STRING
INC HL
LD (STKEND),HL
RET
STKFETCH: LD HL,(STKEND)
DEC HL
LD B,(HL)
DEC HL
LD C,(HL)
DEC HL
LD D,(HL)
DEC HL
LD E,(HL)
DEC HL
LD A,(HL)
STSTKE: LD (STKEND),HL
RET
;FASTER DELETE-TOP-OF-FPCS. TO BE CALLED! THIS IS NOT A FPCS FUNCTION!
;EXIT: HL PTS TO DELETED NUMBER.
FDELETE: LD HL,(STKEND)
LD A,L
SUB 5
LD L,A
LD (STKEND),A
RET NC ;ALWAYS RETS ON STANDARD SAM...
DEC H
JR STSTKE
HLTOFPCS: LD BC,5
LD DE,(STKEND)
LDIR
LD (STKEND),DE
RET
;GET FPCS INTEGER TO BC AND HL. A=C. IOOR IF TOO BIG OR -VE
GETINT: CALL FPTOBC
JR GETIBC
;GET FPCS BYTE TO A AND C. IOOR IF TOO BIG OR -VE
GETBYTE: CALL FPTOA
GETIBC: JR C,IOORERR
RET Z ;RET IF +VE
IOORERR: RST &08
DB 30 ;"Integer out of range"
;COMPRESS TOP OF FPCS TO BC AND HL. CY IF TOO BIG, NZ IF -VE. A=C
FPTOBC: LD HL,(STKEND)
LD BC,-5
ADD HL,BC
LD A,(HL)
AND A ;NC
JR Z,FPBCINT
DB CALC
DB STKHALF
DB ADDN
DB INT ;CHANGES FORM TO INTEGER IF POSSIBLE
DB EXIT
FPBCINT: LD (STKEND),HL ;"DELETE"
XOR A
SUB (HL) ;NC IF SMALL INTEGER FORM (ELSE IOOR)
INC HL
BIT 7,(HL) ;SET NZ IF -VE
INC HL
LD C,(HL)
INC HL
LD B,(HL)
LD A,C
LD H,B
LD L,C
RET Z ;RET IF +VE
RET C ;RET IF OUT OF RANGE
SBC HL,HL ;HL=0
SBC HL,BC ;NEGATE BC. RESULT NZ, CY
CCF
LD B,H
LD C,L
LD A,C
RET ;NEGATED RESULT IN HL/BC. C=A. NZ, NC
;COMPRESS TOP OF FPCS TO A (AND C). CY IF TOO BIG, NZ IF -VE.
FPTOA: CALL FPTOBC
RET C
EX AF,AF'
INC B ;INC B WITHOUT ALTERING THE FLAGS
EX AF,AF'
DJNZ FPTOA2 ;JR IF B<>0 - SIGNAL OUT OF RANGE (CY)
RET
FPTOA2: SCF
RET
;CALLED BY MAINER, INIT
SETMIN: IN A,(URPORT)
PUSH AF
CALL ADDRELN
CALL SETKC2 ;SET KCUR
LD (HL),&0D
INC HL
LD (HL),&FF
INC HL
LD (WORKSP),HL ;CLEAR ELINE
LD (WORKSPP),A
POP AF
OUT (URPORT),A
SETWORK: LD HL,(WORKSP)
LD A,(WORKSPP)
LD (WKEND),HL
LD (WKENDP),A ;CLEAR WORKSPACE
SETSTK: LD HL,(FPSBOT)
LD (STKEND),HL ;CLEAR FLOATING POINT CALC STACK
RET
;SEARCH PROGRAM. CALLED TO FIND DEF FN AND DATA.
;ENTRY: E=TARGET, CHAD PTS TO START
SRCHPROG: LD D,THENTOK ;NULL INTERVENING
SEARCHALL: EXX
LD BC,&FF00+THENTOK ;ALL PROGRAM/NULL TARGET2 RELOAD
EXX
SRCHALL2: LD BC,&0100+THENTOK ;NO INTERVENING/NULL TARGET2
SRCHALL3: RST &18 ;START AT CHAD
LD A,(SUBPPC) ;STAT NO FOR A"
JR FINDERS
;ENTRY AT "FINDER" OR "FINDERS" (WITH A=CURRENT STAT NO)
;B=1 FOR NO INTERVENING TOKENS.
;D=INTERVENING TOKS OR "THEN" FOR NULL, E=TARGET, C=TARGET2 (LESLE OR NULL)
;HL PTS TO START
;C"=TARGET 2 RELOAD, B"=ONE LINE/ALL PROG
;EXIT: CY=FOUND JUST BEFORE HL/(CHAD) AT STAT. A
FINCSTAT: EX AF,AF' ;INC STATEMENT NO. IN A"
INC A
FINDERS: EX AF,AF'
JR FINDER
FSKIP5: INC HL
FSKIP4: INC HL
INC HL
INC HL
INC HL
FINDER: LD A,(HL)
INC HL
CP &0E
JR Z,FSKIP5 ;SKIP FP FORMS
CP &0D
JR Z,FINDER5 ;JR IF LINE END
CP &B7 ;REMTOK
JR Z,FREMARK ;AVOID PROBLEMS FROM EG SINGE QUOTE IN REMS
CP &22 ;QUOTE
JR Z,FQUOTE
CP ":"
JR Z,FINCSTAT ;INC STAT NO
CP THENTOK ;IF COLON OR "THEN"
JR Z,FINCSTAT
CP D
JR Z,FINTERV ;INC "INTERVENING" COUNT IN B IF FOUND
; E.G. "DO" OR "IF" (USE "THEN" AS NULL)
;THEN: JR FINDER4
;TARGET2 IS NULL UNLESS LELSE/LIF
;SEARCH, AND INTERVENING COUNT SHOWS
;NO NESTED LIF-ENDIF STRUCTURES (B=1)
CP C
JR Z,FOUNDY ;JR IF TARGET 2 FOUND
FINDER4: CP E
JP NZ,FINDER ;JR IF NOT TARGET
DJNZ FOUNDX ;JR IF B<>0 - DON"T ACCEPT FIND
FOUNDY: LD (CHAD),HL ;PT CHAD TO TARGET LOCN+1
EX AF,AF' ;A=STAT NO.
SCF ;"FOUND"
RET
FOUNDX: DJNZ FINDN1 ;JR IF COUNT WASN"T 1
EXX ;OR, IF IT WAS, PRIME TARGET2 TO BE NON-NULL
LD A,C ;FETCH TARGET 2 RELOAD FROM C"
EXX
LD C,A
FINDN1: INC B ;CORRECT INTERVENING COUNTER
JR FINDER
FREMARK: LD A,&0D
FREMLP: CP (HL)
INC HL
JP NZ,FREMLP ;LOOP PAST REMS TO LINE END
FINDER5: LD A,(HL) ;MSB OF NEXT LINE NUMBER, OR FF TERMINATOR
EXX
CP B ;B"=00 FOR 1 LINE SEARCH OR FF FOR WHOLE PROG
EXX ;E-LINE NEEDS AN FF TERMINATOR
RET NC ;RET IF FINISHED
BIT 6,H
CALL NZ,INCURPAGE ;INC UPPER RAM PAGE, ADJ HL, IF HL>BFFF
LD (CLA),HL ;CURRENT LINE ADDR
LD A,1 ;STATEMENT 1
EX AF,AF' ;IN A"
JP FSKIP4 ;DO NEXT LINE
FQUOTE: CP (HL)
INC HL
JP NZ,FQUOTE ;LOOP PAST LITERAL STRINGS
JR FINDER ;HL IS PAST END QUOTE
FINTERV: INC B ;INC COUNT OF TARGETS TO SKIP
LD C,THENTOK ;TARGET2=NULL
JR FINDER4
;MAKE ROOM, ALLOWING NO OVERHEAD
MKRMCH: XOR A
PUSH HL
CALL TSTRMBIG
JR MKRM2
;OPEN 1 BYTE AT HL
MKRM1: LD BC,1
;OPEN BC BYTES AT HL. BC MUST BE <4000H
MAKEROOM: XOR A
;OPEN ABC BYTES AT HL. A=16K PAGES, BC=MOD 16K
MKRBIG: PUSH HL ;LOCN
CALL TSTRMBIG
LD HL,150
SBC HL,DE
JP NC,OOMERR ;INSIST ON A 150-BYTE OVERHEAD
MKRM2: LD D,B
LD E,C
LD C,A
LD A,D
AND &3F
LD D,A ;CDE=ROOM. NC (SIGNALS "MAKEROOM")
POP HL ;LOCN
PUSH DE ;MOD 16K
PUSH HL ;LOCN
RST &30
DW XOINTERS ;EXIT WITH AHL=OLD WORKEND (SRC), MOD/PAGCOUNT SET
LD DE,(WKEND)
LD BC,(WKENDP) ;CDE=DEST (NEW WKEND)
CALL FARLDDR
POP DE ;LOCN
POP HL ;MOD 16K
ADD HL,DE
EX DE,HL ;HL=LOCN
DEC DE ;DE=END (IF <16K MADE)
RET
FNORECL: CALL FNDLINE
RET NZ
NORECL: CALL NEXTONE
JR RECLAIM2 ;DELETE LINE FROM PROGRAM
;ENTRY WITH DE=LOCN, HL=END, DE PAGED IN
RECLAIM1: CALL DIFFER ;GET BC, SWOP LOCN TO HL
;ENTRY WITH BC=BYTES TO RECLAIM AT HL (<16K)
RECLAIM2: XOR A
;RECLAIM ABC BYTES AT HL. A=16K PAGES, BC=MOD 16K
RECL2BIG: RES 7,B
RES 6,B
LD D,A
OR B
OR C
RET Z
LD A,D
LD D,B
LD E,C
LD C,A ;CDE=SPACE
PUSH BC ;PAGES
PUSH DE ;MOD 16K
PUSH HL ;LOCN
SCF ;"RECLAIMING"
RST &30
DW XOINTERS ;SETS PAG/MODCOUNT TO MOVE
POP HL ;LOCN
POP DE ;MOD 16K
POP BC ;PAGES
IN A,(251)
PUSH AF
PUSH HL ;LOCN
BIT 6,H
JR Z,RECL5
RES 6,H
INC A
RECL5: CALL ADDAHLCDE ;AHL=SRC
POP DE
POP BC
LD C,B ;CDE=DEST (LOCN)
PUSH DE
CALL FARLDIR
POP HL
RET
;MAKE ROOM AT WKSPACE END, BC BYTES LONG. EXIT WITH BC=ROOM SIZE, DE=START,
;HL=END (IF ROOM <16K), A=UNCHANGED. ROOM PAGE SWITCHED IN.
WKROOM: PUSH AF
CALL TESTROOM ;CHECK BC BYTES OK, GET AHL=NEW WKEND
LD D,A
LD A,(WKENDP)
CALL SELURPG ;SWITCH IN OLD WKEND
LD A,D
LD (WKENDP),A ;NEW WKENDP
LD DE,(WKEND) ;START OF ROOM
LD (WKEND),HL
LD H,D
LD L,E
ADD HL,BC
DEC HL ;END OF ROOM, IF ROOM<16K (HL MAY BE >C000)
POP AF
RET
;ADJUST SINGLE "SYS VAR" (ACTUALLY, FOR-NEXT OR DO/GOSUB/PROC ADDR)
;ENTRY: HL POINTS TO SVAR, CDE=LOCN, F'=CY IF RECLAIMING
ASSV: PUSH HL
POP IY
LD B,1
PNLP: LD A,(IY+0)
LD L,(IY+1)
LD H,(IY+2) ;AHL=SVAR
INC H
DEC H
JR Z,NPSV ;no adj if e.g. eline addr v2.1
;COMPARE AHL AND CDE
BIT 6,H
JR Z,PNT2 ;JR IF IN SECTION C
INC A
RES 6,H ;ELSE ADJUST
PNT2: AND &1F
CP C
JR C,NPSV ;JR IF LOCN PAGE IS HIGHER, SO NO ADJ
JR NZ,PADJ ;JR IF LOCN PAGE IS LOWER - ADJUST
EX DE,HL
SBC HL,DE ;ELSE COMPARE OFFSETS - SBC LOCN,SVAR
ADD HL,DE
EX DE,HL
JR NC,NPSV ;DO NOT ADJUST SVAR IF IT IS <= LOCN
PADJ: PUSH BC ;SAVE PTR COUNT AND LOCN PAGE
PUSH DE
LD BC,(TEMPW4)
LD DE,(TEMPW5) ;CDE=AMOUNT TO ADJ BY
EX AF,AF'
JR C,PRECL ;JR IF RECLAIMING
EX AF,AF'
CALL ADDAHLCDE
JR PNT3
PRECL: EX AF,AF'
CALL SUBAHLCDE
PNT3: POP DE
POP BC
LD (IY+0),A
LD (IY+1),L
LD (IY+2),H ;PLACE ADJUSTED SYS VAR
NPSV: INC IY
INC IY
INC IY
DJNZ PNLP
RET
;ADJUST 'FOR' LOOPS IF LOCN C'D'E' IS BEFORE THEM
AFLPS: EX AF,AF'
LD C,D
LD B,26 ;26 LETTER LISTS
AFML: PUSH HL ;PT TO CURRENT LETTER LIST
AFLL: LD E,(HL)
INC HL
LD D,(HL)
ADD HL,DE
JR C,AFLE ;JR IF THIS LIST ENDED
BIT 6,(HL)
JR Z,AFNF ;JR IF NOT FOR-VAR
PUSH HL
PUSH BC
LD A,(HL)
AND &1F ;NAME LEN-1
ADD A,18 ;3 TO SKIP TO START OF VALUE, 15 FOR VLS
LD E,A
LD D,0
ADD HL,DE ;PT TO ADDR
LD DE,(TEMPW3) ;CDE=LOCN
CALL ASSV ;ADJUST SINGLE "SYSTEM VAR"
POP BC
POP HL
AFNF: INC HL
JR AFLL ;NEXT VAR OF THIS LETTER
AFLE: POP HL ;THIS LIST ENDED NOW
INC HL
INC HL ;PT TO NEXT LIST
DJNZ AFML
EX AF,AF'
RET
ADDRDEST: LD L,(DEST-1)\256
JR ADDRSV
ADDRNV: LD L,(NVARS-1)\256
JR ADDRSV
ADDRNE: LD L,(NUMEND-1)\256
JR ADDRSV
ADDRSAV: LD L,(SAVARS-1)\256
JR ADDRSV
ADDRWK: LD L,(WORKSP-1)\256
JR ADDRSV
ADDRKC: LD A,(KCUR-1)\256
DB &21
ADDRPROG: LD A,(PROG-1)\256
DB &21
ADDRELN: LD A,(ELINE-1)\256
DB &21 ;"JR+2"
;USED BY READ AND ITEM
ADDRDATA: LD A,(DATADD-1)\256
DB &21 ;"JR+2"
ADDRCHAD: LD A,(CHAD-1)\256
LD L,A
;LOOK AT SYS VAR LOCN. ENTRY: HL PTS TO SYS VAR (PAGE, OFFSET)
;EXIT: PAGE SELECTED, HL=OFFSET (IN SECTION C), A=PAGE
ADDRSV: LD H,VAR2/256
;FROM FN, WITH HL=DEFADDRP
ASV2: LD A,(HL)
CALL SELURPG
INC HL
LD A,(HL)
INC HL
LD H,(HL)
LD L,A
IN A,(251)
AND &1F
RET
NEXTONE: PUSH HL
INC HL
INC HL
LD C,(HL)
INC HL
LD B,(HL) ;LINE LEN
INC HL
ADD HL,BC
POP DE ;DE=OLD START, HL=NEXT LINE START
DIFFER: AND A
SBC HL,DE
LD B,H
LD C,L
ADD HL,DE
EX DE,HL
RET
;ENTRY AS LIMBYTE, BUT FPCS VALUE DECED BEFORE CHECKING, RETURNED DECED. C IS
;NOT DECED
LIMDB: LD A,&FF
DB &FE ;"JR+1"
;ENTRY: D=LIMIT (VALUE MUST BE BELOW IT), E=ERROR TO GIVE IF VALUE TOO HIGH.
;VALUE IS ON FPCS
;EXIT: A AND C=VALUE, DE=ORIG
LIMBYTE: XOR A
PUSH AF
PUSH DE
CALL FPTOA
POP DE ;LIMIT/ERROR
JR C,ERRORE ;JR IF >FF
JR NZ,ERRORE ;JR IF -VE
POP AF
ADD A,C
CP D
RET C
ERRORE: LD HL,ERRNR
LD (HL),E
PUSH HL ;WILL BE POPPED AND USED AS "RET ADDR"
JP &0008
;SET PAGCOUNT/MODCOUNT FROM BC (0000-FFFF)
SPLITBC: PUSH AF
LD A,B
RES 7,B
RES 6,B
LD (MODCOUNT),BC ;LEN MOD 16K
RLCA
RLCA
AND &03
LD (PAGCOUNT),A ;PAGES (0-3)
POP AF
RET
;GET ROOM. RETURN FREE MEMORY (UPPER RAMS) IN AHL AS A 19 BIT NO. NZ IF >=64K
GETROOM: PUSH BC
PUSH DE
CALL WENORMAL
GRM2: LD C,A
EX DE,HL ;CDE=WKSPACE END
CALL RTNORMAL ;AHL=RAMTOP (19 BIT)
SCF
SBC HL,DE
SBC A,C
POP DE
POP BC
RET ;AHL=ROOM (19BIT). NZ IF ROOM >=64K
;PAGE OVERFLOW. USED BY INSTRING, S16OP
;CALLED IF ADD HL,RR GIVES CARRY. CORRECTS THE PAGE AND ADDRESS IN HL
;ENTRY: HL=0000-BFFE (BFFE IF HL WAS BFFF+FFFF)
PGOVERF: IN A,(URPORT)
CALL PGOA
JR PGOE
;CORRECT AHL AFTER PAGE OVERFLOW, BUT DON"T ALTER PAGING
PGOA: ADD A,2 ;IF THERE WAS A CARRY, ADDR IS AT LEAST 0000
;SO INC 2 PAGES SO ADDR CAN BE DROPPED 32K
BIT 6,H ;IF BIT 6 IS HIGH WE CAN INC AGAIN
JR Z,PGOA2
RES 6,H
INC A
PGOA2: BIT 7,H
JR Z,PGOA3 ;IF BIT 7 IS HIGH INC TWICE
ADD A,2
PGOA3: SET 7,H
RET
;ADDRESS ELINE AND DEC PTR TO PT TO SAVARS END
ADDRELND: CALL ADDRELN
;ENTRY: HL HOLDS AN ADDRESS. IT IS DECREMENTED, AND ADJUSTED IF IT FALLS
;TOO LOW, SO IT PTS TO 8000-BFFF, PAGING AS NEEDED. IF CALLED FROM SYNTAX4,
;HL MAY BE BELOW 8000H ALREADY. COPES WITH UNDERFLOW OF UP TO 32K
DECPTR: DEC HL
CHKPTR: BIT 7,H
RET NZ ;RET IF STILL AT 8000H OR MORE
IN A,(251)
DEC A
SET 7,H
BIT 6,H
JR NZ,DECPT2 ;JR IF FALLEN INTO 4000-7FFF - CORRECT BY 1 PAGE
DEC A ;IF IN 0000-3FFF, 2 PAGES
DECPT2: RES 6,H
PGOE: OUT (251),A
RET
;ADD ADDR,BC. ADD BC TO AN ADDRESS IN AHL. A=PAGE, HL=8000-BFFF. BC UNCHNGED.
;BC CAN HAVE ANY VALUE
;SUB ADDR,BC. DITTO
;CARRY IF OVERFLOW
ADDAHLBC: CALL AHLNORM ;GET 19 BIT FORM IN AHL
ADD HL,BC
ADC A,0 ;ADD AHL,BC
JR PAGEFORM
SUBAHLBC: CALL AHLNORM
AND A
SBC HL,BC
SBC A,0 ;SUB AHL,BC
JR PAGEFORM
;ADD ADDR IN AHL (PAGE FORM) TO THE ADDRESS IN CDE (PAGE FORM)
;RESULT IN AHL (PAGE FORM). CARRY IF OVERFLOW PAGES. CDE UNCHANGED.
ADDAHLCDE: PUSH BC
PUSH DE
CALL TWOCONV
ADD HL,DE
ADC A,C
JR PPFCOM
;SUBTRACT FROM ADDR IN AHL (PAGE FORM) THE ADDRESS IN CDE (PAGE FORM)
;RESULT IN AHL (PAGE FORM). CARRY IF OVERFLOW. CDE UNCHANGED.
SUBAHLCDE: PUSH BC
PUSH DE
CALL TWOCONV
AND A
SBC HL,DE
SBC A,C ;SUB AHL,CDE
PPFCOM: POP DE ;CONTINUE INTO PAGEFORM
POP BC
;TRANSFORM 19-BIT NUMBER IN AHL TO PAGE, ADDR (8000-BFFF)
PAGEFORM: RL H
RLA
RL H
RLA ;NC. PAGE NOW OK
RR H
SCF
RR H ;ADDR NOW OK IN 8000-BFFF FORM
CP &20
CCF ;SET CARRY IF OVERFLOW
RET;CONVERT PAGE FORMS IN AHL AND CDE TO 19-BIT. USES B
TWOCONV: CALL AHLNORM
;CONVERT PAGE FORM IN CDE TO 19-BIT IN CDE. CHANGES CDE ONLY
CDENORM: PUSH AF
EX DE,HL
LD A,C
CALL AHLNORM
EX DE,HL
LD C,A
POP AF
RET
RTNORMAL: LD A,(RAMTOPP)
LD HL,(RAMTOP)
JR AHLNORM
WENORMAL: LD A,(WKENDP)
LD HL,(WKEND)
BIT 6,H
JR Z,AHLNORM
INC A
;CONVERT PAGE FORM IN AHL TO 19-BIT IN AHL.
;TOP 3 BITS OF ORIG A AND TOP 2 BITS OF HL ARE IRREL.
AHLNORM: RLC H
RLC H
RRA
RR H
RRA
RR H
AND &07
RET
;SET ERROR STACK PTR. EXITS WITH OLD ERRSP ON STACK. AFTER A ROUTINE HAS CALLED
;HERE, IT CAN CALL OTHER SRS. AND RETURN WILL STILL OCCUR EVEN AFTER AN ERROR.
;USES HL ONLY
SETESP: LD HL,(ERRSP)
EX (SP),HL
PUSH HL
LD (ERRSP),SP
RET
;READ LEN FROM "DESIRED" HEADER (TAPE)
RDRLEN: LD L,(HDR+HDN+3)\256
DB &11 ;"JR+2"
;READ LEN FROM LOADED HEADER
RDLLEN: LD L,(HDL+HDN+3)\256
LD H,HDR/256
;READ THREE BYTES FROM HL INTO C AND DE
RDTHREE: LD C,(HL)
INC HL
LD E,(HL)
INC HL
LD D,(HL)
RET
EDGE2: LD C,0 ;INIT LOOP COUNTER TO 0
EDGEC: CALL EDGSENS ;FIND AN EDGE
RET NC ;RET IF BREAK OR TIMEOUT
AND A ;NC
EDGSENS: LD A,8 ;DELAY TO AVOID DOUBLE COUNTS, RELATED TO SPEED
EWL: DEC A
JR NZ,EWL
EDGLP: IN A,(KEYPORT)
INC C
RET Z ;TIMEOUT - NC, Z
XOR B ;CP EAR BIT
AND &40 ;WITH LAST EDGE TYPE
LD A,B
JR Z,EDGLP ;LOOP UNTIL SIGNAL LEVEL CHANGES. 47 Ts PER LOOP
;(LENGTHENED TO NEAR MULTIPLE OF 8)
XOR &67
LD B,A ;FLIP "LAST EDGE TYPE" (BIT 6)
;FLIP BORDER (BITS 2-0)
;KEEP MIC (BIT 3) UNCHANGED (HI)
;KEEP BEEP (BIT 4) UNCHANGED
;KEEP SOF (BIT 7) UNCHANGED
AND &1F ;SOFF BIT (BIT 7) LOW
;THRO MIDI (BIT 6) LOW
;BORDER MSB (BIT 5) LOW
OUT (KEYPORT),A ;ALTER BORDER
LD A,&F7
IN A,(STATPORT) ;BIT 5 IS LOW IF ESC PRESSED
RLCA
RLCA
RLCA
LD A,C ;A AND C HOLD LENGTH OF PULSE
RET ;CY="OK", NC=ESC.