Commodore 1541-II - Chapter 9: Machine Language Programs; Disk-Related Kernafl Subroutines

CHAPTER 9
MACHINE LANGUAGE PROGRAMS
Here is a list of disk-related Kernal ROM subroutines and a practical example of their
use in a program which reads a sequential file into memory from disk. Note that 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.
DISK-RELATED KERNAL SUBROUTINES
Label
Address
Function
SETLFS
SETNAM
OPEN
CLOSE
CHKIN
CHKOUT
CLRCHN
CHRIN
CHROUT
START
NEXT
END
=
=
=
=
=
=
=
=
LDA
LDX
LDY
JSR
LDA
LDX
LDY
JSR
JSR
LDX
JSR
JSR
BEQ
JSR
JMP
LDA
JSR
JSR
RTS
$FFBA
$FFBD
$FFC0
$FFC3
$FFC6
$FFC9
$FFCC
$FFCF
$FFD2
#4
#<FNADR
#>FNADR
SETNAM
#3
#8
#0
SETLFS
OPEN
#3
CHKIN
CHRIN
END
CHROUT
NEXT
#3
CLOSE
CLRCHN
;SET LOGICAL, FIRST & SECOND ADDRESSES
;SET LENGTH & ADDRESS OF FILENAME
;OPEN LOGICAL FILE
;CLOSE LOGICAL FILE
;SELECT CHANNEL FOR INPUT
;SELECT CHANNEL FOR OUTPUT
;CLEAR ALL CHANNELS & RESTORE
DEFAULT I/O
;GET BYTE FROM CURRENT INPUT DEVICE
;OUTPUT BYTE TO CURRENT OUTPUT
DEVICE
;SET LENGTH & ADDRESS
;OF FILE NAME, LOW
;& HIGH BYTES
;FOR NAME SETTER
;SET FILE NUMBER,
;DISK DEVICE NUMBER,
;AND SECONDARY ADDRESS
;AND SET THEM
;OPEN 3,8,0,t4TEST"
;SELECT FILE 3 FOR INPUT
;GET NEXT BYTE FROM FILE
;UNTIL FINISH OR FAIL
;OUTPUT BYTE TO SCREEN
;AND LOOP BACK FOR MORE
;WHEN DONE
;CLOSE FILE
;RESTORE DEFAULT I/O
;BACK TO BASIC
FNADR .BYT "TEST" ;STORE FILE NAME HERE
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