Commodore 1541-II - Reading the Error Channel

FORMAT FOR SENDING DISK COMMANDS
OPEN 15,device#,15,command$
or
Print# 15, commands
Examples:
OPEN 15,8,15, "VO"
or
PRINT#15,"VO"
where "device #" is the disk's device number, normally 8, and "command$" is any
valid string expression. If it is not also a valid disk command, it will result in an error on
the disk drive. This is indicated by a flashing error light on the disk drive, and an error
message such as "31,SYNTAX ERROR" when the error channel is read as described on
the next two pages.
READING THE ERROR CHANNEL: BASIC 2
In Basic 2, there is no simple way to learn what is causing the error light to flash on
the disk drive without writing a small program. This, in turn, causes you to lose any
program variables already in memory. The reason for this is that the INPUT# command
cannot easily be used in immediate mode (that is, without a line number).
You will often need to be able to read the disk error channel, to see why the disk error
light is flashing, and thereby turn the error light off again.
Here is a brief program to check for disk errors:
10J3PEN 15,8,15
20 INPUT#15,EN,EM$,ET,ES
30 PRINT EN,EM$,ET,ES
40 CLOSE 15
This little program reads the error channel into 4 Basic variables, and prints the
results on the screen. A message will be displayed whether there is an error or not, but if
there was an error, this program will also clear it from disk memory and turn off the error
light on the disk drive.
Once the message is on the screen, you can look it up in Appendix B to see what it
means, and what to do about it.
READING THE ERROR CHANNEL: BASIC 3.5
In Basic 3.5, it is very easy to learn what is causing the error light to flash on the disk
drive, and no need to write a program. Simply type:
26