Commodore 1581 - Chapter 8: Machine Language Programs; Disk-Related Kernal Subroutines

CHAPTER 8
MACHINE LANGUAGE PROGRAMS
Here is a list of host computer disk-related Kernal ROM subrou
tines and a practical example of their use in a program that reads a
sequential file into memory from disk. Most require advance setup of
one or more processor registers or memory locations and all are
called with the assembly language JSR command.
For a more complete description as to what each routine does
and how parameters are set for each routine, see the Programmer's
Reference Guide for your specific computer.
Label
DISK-RELATED KERNAL SUBROUTINES
Address
Function
SETLFS = $FFBA ;SET LOGICAL, FIRST & SECOND ADDRESSES
SETNAM = $FFBD ;SET LENGTH & ADDRESS OF FILENAME
OPEN = $FFC0 ;OPEN LOGICAL FILE
CLOSE = $FFC3 ;CLOSE LOGICAL FILE
CHKIN = $FFC6 ;SELECT CHANNEL FOR INPUT
CHKOUT = $FFC9 ;SELECT CHANNEL FOR OUTPUT
ORCHN = $FFCC ;OEAR ALL CHANNELS & RESTORE
DEFAULT I/O
CHRIN = $FFCF ;GET BYTE FROM CURRENT INPUT DEVICE
CHROUT = $FFD2 ;OUTPUT BYTE TO CURRENT OUTPUT
DEVICE
START LDA #4 ;SET LENGTH & ADDRESS
LDX #<FNADR ;OF FILE NAME, LOW
LDY #>FNADR ;& HIGH BYTES
JSR SETNAM ;FOR NAME SETTER
LDA #3 ;SET FILE NUMBER
LDX #8 ;DISK DEVICE NUMBER
LDY #0 ;AND SECONDARY ADDRESS
JSR SETLFS ;AND SET THEM
JSR OPEN ;OPEN 3,8,0,"TEST"
LDX #3
JSR CHKIN ;SELECT FILE 3 FOR INPUT
NEXT JSR CHRIN ;GET NEXT BYTE FROM FILE
BEQ END jUNTEL FINISH OR FAIL
JSR CHROUT ;OUTPUT BYTE TO SCREEN
JMP NEXT AND LOOP BACK FOR MORE
END LDA #3 ;WHENDONE
JSR CLOSE ;CLOSE FILE
JSR CLRCHN ;RESTORE DEFAULT I/O
RTS ;BACK TO BASIC
FNADR .BYT "TEST" ;STORE FILE NAME HERE
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