MAP1 IN'CHR,X,1
	MAP1 DISK'FSPEC,S,24
	MAP1 IN'UNIT,F,,0
	MAP1 OUT'UNIT,F,,0
	MAP1 DISK'UNIT,F,,3
	MAP1 ERROR'UNIT,F,,4
!	MAP1 COM'FSPEC,S,24
	MAP1 SOH,X,1,CHR$(1)
	MAP1 CTRLC,X,1,CHR$(3)
	MAP1 EOT,X,1,CHR$(4)
	MAP1 ACK,X,1,CHR$(6)
	MAP1 NAK,X,1,CHR$(21)
	MAP1 CHECK'SUM,F
	MAP1 BLOCK'LENGTH,F,,128
	MAP1 IO'REC,X,128
	MAP1 BLOCK'COUNT,F,,1
	MAP1 NEXT'NAK,F
	MAP1 I,F

	INPUT LINE "Receive fspec?",DISK'FSPEC
	XCALL IMG
	OPEN #DISK'UNIT, DISK'FSPEC, OUTPUT
!	INPUT LINE "Communications trmdef?",COM'FSPEC
!	COM'FSPEC = ""
!	OPEN #IN'UNIT, "TRM:"+COM'FSPEC, INPUT
!	OPEN #OUT'UNIT, "TRM:"+COM'FSPEC, OUTPUT

FLUSH'BUFFER:
	IF EOF(IN'UNIT) GOTO START'NAKING
	INPUT LINE #IN'UNIT, IN'CHR
	GOTO FLUSH'BUFFER

START'NAKING:
	NEXT'NAK = TIME
NEXT'NAK'LOOP:
	IF EOF(IN'UNIT) = 0 GOTO LOOK'FOR'SOH
	IF NEXT'NAK > TIME GOTO NEXT'NAK'LOOP
	PRINT #OUT'UNIT, NAK;
	NEXT'NAK = TIME+10
	GOTO NEXT'NAK'LOOP
	
LOOK'FOR'SOH:
	INPUT LINE #IN'UNIT, IN'CHR
	IN'CHR = CHR$(ASC(IN'CHR) AND 127)
	IF IN'CHR = CTRLC GOTO CTRLC'ABORT
	IF IN'CHR = EOT GOTO EOT'FOUND
	IF IN'CHR <> SOH GOTO START'NAKING
!	IF IN'CHR <> SOH &
		PRINT #0,"?";ASC(IN'CHR);IN'CHR; : &
		GOTO START'NAKING
	INPUT LINE #IN'UNIT, IN'CHR
	IF ASC(IN'CHR) <> BLOCK'COUNT GOTO BAD'BLOCK'COUNT
	INPUT LINE #IN'UNIT, IN'CHR
	IF 255-ASC(IN'CHR) <> BLOCK'COUNT GOTO BAD'BLOCK'COUNT
	CHECK'SUM = 0
	INPUT LINE #IN'UNIT, IO'REC
	FOR I = 1 TO BLOCK'LENGTH
	CHECK'SUM = CHECK'SUM+ASC(IO'REC[I;1])
	NEXT
	INPUT LINE #IN'UNIT, IN'CHR
	IF ASC(IN'CHR) <> (CHECK'SUM AND 255) GOTO BAD'CHECK'SUM
	PRINT #DISK'UNIT, IO'REC;
	BLOCK'COUNT = BLOCK'COUNT+1
	PRINT #OUT'UNIT, ACK
	GOTO LOOK'FOR'SOH

BAD'BLOCK'COUNT:
	GOTO START'NAKING

EOT'FOUND:
	PRINT #OUT'UNIT, ACK;
	END

CTRLC'ABORT:
	END

BAD'CHECK'SUM:
	GOTO START'NAKING