cbmsrc/MONITOR_C64/last at master · mist64/cbmsrc · GitHub

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	.SKIP 4
	*= BEGIN
COLDS	JMP INIT ;COLD START MONITOR
WARMS	JMP BRKE ;WARM START MONITOR
	.SKIP 3
RDT	JMP BASIN ;ALL INPUT THRU HERE
WRT	JMP BSOUT ;ALL OUTPUT THRU HERE
	.SKIP 3
; INSTALL EXTRA MONITOR COMMANDS
;
INIT	SEI ;STOP IRQ'S
	LDA WWLK ;INIT NEW BRK VECTOR
	LDX WWLK+1
	STA CBINV
	STX CBINV+1
	LDA CINV ;GET OLD IRQ VECTOR
	LDX CINV+1
	CMP WINTR ;CHANGED ALREADY ?
	BNE INIT10 ;NO - GO CHANGE
	CPX WINTR+1
	BEQ INIT20 ;YES - LEAVE BE
INIT10	STA KEYS
	STX KEYS+1
	LDA WINTR ;INSTALL REPEAT KEYS
	LDX WINTR+1
	STA CINV
	STX CINV+1
INIT20
	LDA WCOLDS
	LDX WCOLDS+1
	CPX #$80 ;IN ROM ABOVE SCREEN ?
	BCS INIT30
	STA MEMSIZ
	STX MEMSIZ+1
INIT30	LDA #$10 ;SET DELAYS FOR REPEAT
	STA DELAY
	STA REPDY
	LDA #0
	STA WSW ;DO A BREAK
	STA RBUSY ;NOT BUSY
	CLI ;ALLOW IRQ'S
	BRK
	.SKIP 4
BRKE
	SEC
	LDA PCL ;BACK UP ONE BYTE
	SBC #1
	STA PCL
	LDA PCH
	SBC #0
	STA PCH
B5	JSR CRLF
	LDX #'B  ;SET X EQUAL TO B
B567	LDA #'*
	JSR WRTWO
	LDA #'R ;SET FOR R DISPLAY TO
;                      PERMIT IMMEDIATE
;                      ALTER FOLLOWING
;                      BREAKPOINT
	BNE NWCMD ;ALWAYS
ERROPR	LDA #$3F ;PRINT A "?" FOR AN ERROR
	JSR WRT
STRT
	JSR CRLF
STRT10	LDA #'. ;TYPE A PROMPTING '.'
	JSR WRT
	LDA #0 ;ZERO WRAP FLAG
	STA WRAP
	STA RBUSY ;NOT BUST NOW
	LDX #$FF ;RESET THE STACK
	TXS
ST1	JSR RDOC ;READ COMMAND. CHARACTER
;                      IS RETURNED IN A
	CMP #'. ;IGNORE PROMPTING '.'
	BEQ ST1
	CMP #$20 ;IGNORE SPACES
	BEQ ST1
	.SKIP 3
; SEARCH FOR COMMANDS
;
NWCMD	LDX #NCMDS-1
NW10	CMP CMDS,X
	BNE NW20
	STA SAVCMD
	TXA ;MULT BY TWO
	ASL A
	TAX ;INDEX INTO DISPATCH TABLE
	.SKIP 3
; DISPATCH TO COMMAND
;
	LDA ADRS,X ;FAKE INDEXED JMP
	STA TMP0
	LDA ADRS+1,X ;PUSH ADR-1 AND RTS
	STA TMP0+1
	JMP (TMP0)
;
NW20	DEX
	BPL NW10
	BMI ERROPR ;CMD NOT FOUND ERROR
	.SKIP 3
; DEC TMP0 OR TMP2
;
DECT2	LDX #2 ;DEC TMP2 WORD
	BNE DEC30 ;ALWAYS
DECT0	LDX #0 ;DEC TMP0 WORD
DEC30	LDY TMP0,X ;A BORROW?
	BNE DEC20 ;NO-SKIP
	LDY TMP0+1,X ;A MEMORY WRAP
	BNE DEC10 ;NO-SKIP
	INC WRAP ;YES-SET FLAG
DEC10	DEC TMP0+1,X
DEC20	DEC TMP0,X
DRTS	RTS
	.SKIP 3
;DISASSEMBLE ONE LINE PRINT 9 SPACES
;
DISSPC	LDA #0 ;PRINT ALL CHARS
	STA PTCH
	JSR DIS300 ;DIS. ONE
	LDX #9 ;SET FOR 9 SPACES
	.SKIP 3
;PRINT # OF SPACES=X
;
SPCX	JSR SPACE
	DEX
	BNE SPCX
	RTS
	.SKIP 3
; EXCHANGE TMP REGISTERS
;
T0T10	LDX #2 ;EXCHANGE TMP0 WITH
T0T100	LDA TMP0-1,X ; TMP10
	PHA
	LDA TMP10-1,X
	STA TMP0-1,X
	PLA
	STA TMP10-1,X
	DEX
	BNE T0T100
	RTS
	.SKIP 3
; DOUBLE SUBTRACT
; DIFF=LO DIFFERENCE
; Y=HI DIFFERENCE
; A=0 IF ZERO DIFFERENCE
;
DCT10	LDA TMP10 ;TMP10-TMP0
	LDY TMP10+1
	JMP DC10 ;SKIP OVER
DCMP	LDA TMP2 ;TMP2-TMP0
	LDY TMP2+1
DC10	SEC
	SBC TMP0
	STA DIFF
	TYA ;HI BYTE IN Y
	SBC TMP0+1
	TAY ;SAVE HI RESULT IN Y
	ORA DIFF ;OR LO FOR EQUAL TEST
	RTS
	.SKIP 5
	.END