Commodore Plus 4 - Page 371

The Disk Drive
359
3. Call CIOUT ($FFA8) to send bytes from .A.
4. Call UNLSN ($FFAE).
Example:
Closing a File
1. Load .A with the device number of the disk drive. Call LISTN ($FFB1).
2. Load .A with the disk drive channel number you want to close ORed with $E0
(to indicate close this channel). Call SECND ($FF93).
3. Call UNLSN ($FFAE).
This example reads the first sector of the directory of a diskette and places it in
memory. Errors are detected and acted on, but no user interface is in place to
deliver error messages to the user.
2000
2002
2004
2006
2008
200B
200E
2010
2012
2015
2017
201A
201D
201F
2022
2024
2027
2029
202C
202F
2030
2032
2034
2037
2039
203C
203E
2041
2043
2046
2049
204A
204D
204F
2052
2055
A9
85
A9
85
20
20
D0
A9
20
A9
20
20
A9
20
A9
20
A2
BD
20
E8
E0
90
20
A9
20
A9
20
A2
20
9D
E8
20
F0
20
AD
0D
00
90
08
AE
Bl
B7
7B
F2
93
23
A8
AE
08
Bl
FF
93
00
00
A8
0B
F5
AE
08
B4
6F
96
00
A5
00
B7
F4
AB
00
01
FF
FF
FF
FF
FF
FF
FF
21
FF
FF
FF
FF
FF
23
FF
FF
23
23
LDA
STA
LDA
STA
JSR
JSR
BNE
LDA
JSR
LDA
JSR
JSR
LDA
JSR
LDA
JSR
LDX
LDA
JSR
INX
CPX
BCC
JSR
LDA
JSR
LDA
JSR
LDX
JSR
STA
INX
JSR
BEQ
JSR
LDA
ORA
#$00
$90
#$08
$AE
$FFB1
$FFB7
$208B
#$F2
$FF93
#$23
$FFA8
$FFAE
#$08
$FFB1
#$FF
$FF93
#$00
$2100,X
$FFA8
#$0B
$2029
$FFAE
#$08
$FFB4
#$6F
$FF96
#$00
$FFA5
$2300,X
$FFB7
$2043
$FFAB
$2300
$2301
Clear the status variable.
Disk drive device number.
Store in the current device number.
Tell drive to listen.
Read status variable.
If not zero, then error.
Open command for channel 2.
Send as secondary address to drive.
This is the code for a pound sign (#)
Open a direct-access channel.
Tell drive to stop listening.
Disk drive device number.
Tell drive to listen.
Open command for channel 15.
Send as secondary address to drive.
.X counts bytes to send.
Get a byte of the Ul command.
Send to the drive.
Increment count.
Compare to length of Ul command.
Not done, continue sending.
Tell drive to stop listening.
Disk drive device number.
Tell drive to talk.
Access conmand channel (for errors).
Send as secondary address to drive.
.X counts the bytes received.
Receive a byte from the drive.
Store in error buffer.
Increment byte count.
Read status variable.
If zero, more to receive so go back.
Tell drive to stop talking.
Get first byte of error buffer.
OR with the second byte.