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From: emjej@uokvax.UUCP
Newsgroups: net.micro.6809
Subject: Re: Request for os9 info
Message-ID: <3500138@uokvax.UUCP>
Date: Fri, 28-Mar-86 10:18:00 EST
Article-I.D.: uokvax.3500138
Posted: Fri Mar 28 10:18:00 1986
Date-Received: Tue, 1-Apr-86 07:47:50 EST
References: <8700004@hpvcla>
Lines: 39
Nf-ID: #R:hpvcla:8700004:uokvax.UUCP:3500138:000:2109
Nf-From: uokvax.UUCP!emjej    Mar 28 09:18:00 1986


/* Written 10:39 am  Mar 17, 1986 by davel@hpvcla in net.micro.6809 */
>What happens to os9 if it gets handed a character with the most significant
>bit set?  My input driver carefully strips the bit before passing the 
>character on. The keyboard I have has several special function keys and I
>have thought I could flag these keys with the most significant bit.

OS-9 is perfectly willing to pass 8-bit data along.  (I found this out the
hard way on a VT-200 compatible terminal talking to Unix, which seems to
insist on sending stuff out with even parity! :-)  Your driver could,
however, check the PD option section to decide whether to strip the
parity bit.

>The documentation of getsta/setsta is somewhat confusing. If I remember
>correctly the section on the getsta/setsta driver entry points claims
>that RBF and SCF handle all current status requests. Implying that the
>driver need not worry. Of course this is not true.  The device ready status
>request is at least one that the driver needs to handle.

If the docs say that, then something's hosed.  The idea behind get/setstat
is that at each level in the Great Chain of Being (IOMAN -> file manager
-> device driver), those get/setstat requests that should be handled are
handled, and any others are passed on down.  For example, IOMAN can handle
the "copy the PD option section" request; RBFMAN handles record locking;
as you point out, device drivers have to support things like device ready.

>New documentation would likely explain when and how
>the getsta entry should return the number of bytes available to be read.

Let me strongly urge that you get a copy of *The Complete *Rainbow* Guide
to OS-9* by Dale L. Puckett and Peter Dibble, available at your local Radio
Shack or from *Rainbow* magazine.  It contains listings of sample device
drivers.  Basically, the ACIA driver they show keeps a queue of characters
waiting to be read which is added to (or a 244, device overrun, error is
signalled) if the interrupt service routine snarfs a character from the
device.

						James Jones
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