[Info-vax] Timeout in a write using QUIW.

[Phil Howell]

On Thursday, 22 June 2023 at 7:36:54 am UTC+10, Jan-Erik Söderholm wrote:
> Den 2023-06-21 kl. 23:25, skrev Stephen Hoffman: 
> > On 2023-06-21 20:45:12 +0000, Jan-Erik S derholm said: 
> > 
> >> Now, here is a technical one... 
> >> 
> >> When doing a *read* from a terminal device using QIOW, one 
> >> can use IO$M_TIMED and supply a timeout value in P3. That 
> >> works perfectly and we use that a lot... 
> >
> > I've never had great success... 
> 
> 
> I'm sorry about that. As I wrote, it works perfectly. In the 
> case of reads, of course, where it is supported. 
> 
> My question was about writes, and it has been confirmed that 
> timeout paramaters are not supported there. Thanks Arne. 
> 
> Now we need to weight the coding work against getting 
> network cables installed to the printers. Wired printers 
> will also "solve" the issue with the current code. We have 
> 15-20 older similar Zebra label printers, all wired, and 
> we do not see these error scenarios with those. 
> All using the same C routine for the QIOW calls. 
> 
> 
> Jan-Erik.
While you cannot request a timeout on a WRITEVBLK
you may be able to workaround this by using READPROMPT
With this you get two i/o's in one call,
the first is a write of your "prompt" followed by a read on the same channel.
If you set up your "prompt" as the content of your label then do the qio call
it should write this to the device, then do the read, which you can check or ignore.
If you get a tt_timeout, then wait a bit and retry.
The most concise explanation of this is in wikipedia on the qio page.
The I/O user manual just goes on and on
You may have to increase the size of the typeahead buffer to cater for the size of your label
as well as managing all the usual qio stuff like buffer lengths, IOSBs, terminator masks, ASTs, etc.

If I was retiring in a couple of weeks I would recommend cabling up all the printers,
but it could be an interesting way of getting your successor to hate you?

Phil