Low level SIO commands

[danwinslow]

I would like some advice about the best way to generate custom SIO commands on the bus..ie., device/command/parm1/parm2/checksum. I was thinking that XIO could be used, but I am not really sure about that. I guess I could go find the actual IOCB and fill it out, but can I do that and JSR to some routine without messing things up? The basic thing I want to do is to be able to send custom SIO commands to arbitrary devices. Just looking for advice on the best way to approach. I am using cc65.

Edited June 15, 2005 by danwinslow

[ijor]

Just use SIO ($E459), it's very simple. Or I misunderstand your question?

 

You can't use XIO and IOCB, they are CIO level stuff.

[danwinslow]

So fill out an IOCB and JSR to $E459?

[ijor]

Not IOCB. Again, IOCB is a CIO structure. SIO uses the "DCB" structure at $300. See the "Operating System's User Manual" in the Technical Notes for details. Or numerous other references.

 

But a quick info:

 

$300: Device Id

$301: Unit number

$302: Command

$303: Frame direction on Input. Status on Output

$304/5: Buffer address

$306: Timeout in seconds.

$307: Unused

$308/9: Frame length

$30A/B: Auxiliary bytes

 

I think everything if self-explanatory except:

 

$303 on input specifies if it's a read ($40), write ($80), or no data frame $(00).

The actual device id transmitted over the SIO bus is constructed by adding both values in $300 and $301 and substracting 1.

 

Unlike CIO, you don't have to setup any CPU registers before calling SIO (there is only one DCB). Status result is both in $303 and the Y register.

[danwinslow]

Thanks, Ijor, very good info. Also reading up on it in the refernces.