Commodore Plus 4 - Page 369

The Disk Drive
3S7
2071 B0 03 BCS $2076
2073 20 A0 20 JSR $20A0
2076 20 E7 FF JSR $FFE7
2079 00 BRK
Check for I/O errors.
Check the disk error channel.
Make sure all files are closed.
Stop processing.
The following subroutine reads the disk error channel. If two zero characters
are received, then there is no error, and it exits. If not, the message is displayed,
the files are closed, and the stack pointer is restored to its proper value. Processing
is then stopped.
. 20A0 A9 01 LDA #$01
. 20A2
. 20A4
. 20A6
. 20A9
. 20AB
. 20AE
. 20B1
. 20B3
. 20B5
. 20B8
. 20BA
. 20BD
. 20BF
. 20C1
. 20C4
. 20C6
. 20C8
. 20CA
. 20CD
. 20CF
. 20D2
. 20D3
. 20D6
. 20D9
. 20DB
. 20DE
. 20E1
• 20E4
. 20E6
. 20E8
. 20EB
. 20EC
. 20ED
A2
A0
20
A9
20
20
B0
A2
20
B0
20
C9
D0
20
C9
D0
A9
20
B0
20
60
20
20
A9
20
20
20
C9
D0
20
68
68
00
08
0F
BA
00
BD
C0
35
01
C6
2E
CF
30
12
CF
30
0E
01
C3
19
CC
CF
CF
0D
D2
CF
D2
0D
F6
E7
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
FF
LDX
LDY
JSR
LDA
JSR
JSR
BCS
LDX
JSR
BCS
JSR
CMP
BNE
JSR
CMP
BNE
LDA
JSR
BCS
JSR
RTS
JSR
JSR
LDA
JSR
JSR
JSR
CMP
BNE
JSR
PLA
PLA
BRK
#$08
#$0F
$FFBA
#$00
$FFBD
$FFC0
$20E8
#$01
$FFC6
$20E8
$FFCF
#$30
$20D3
$FFCF
#$30
$20D6
#$01
$FPC3
$20E8
$FFCC
$FFCF
$FFCF
#$0D
$FFD2
$FFCF
$FFD2
#$0D
$20DE
$FFE7
Logical file number to use for command
channel.
Device number of disk drive.
Command channel.
SETLFS.
No file name required.
SETNAM.
OPEN.
Check for I/O errors.
Logical file number of channel.
Set up as input channel.
Check for I/O errors.
Get a character.
Compare to a zero character.
If not, there is an error.
Get a character.
Compare to a zero character.
If not, there is an error.
Logical file number of channel.
Close the file.
Check for I/O errors.
Return I/O channels to defaults.
Return from subroutine with no error.
Get a character.
Get a character.
Carriage return character.
Send to screen.
Get a character from the error channel.
Send to screen.
Compare to a carriage return.
If not, continue.
Close down all files and restore I/O
channels•
Pull the return address off the stack.
Stop processing.
The file name must be in memory at $2100.
>S1OO 44 41 54 46 49 40 SC 53 :
>S108 2C 57 00 00 00 00 00 00 :