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From: davel@hpvcla.UUCP
Newsgroups: net.micro.6809
Subject: Request for os9 info
Message-ID: <8700004@hpvcla.UUCP>
Date: Mon, 17-Mar-86 12:39:00 EST
Article-I.D.: hpvcla.8700004
Posted: Mon Mar 17 12:39:00 1986
Date-Received: Sun, 23-Mar-86 00:30:37 EST
Lines: 35
Nf-ID: #N:hpvcla:8700004:000:1754
Nf-From: hpvcla!davel    Mar 17 10:39:00 1986



I have been looking at some os9 drivers, one has some features I would like
to fix. In the process of trying to understand them, I have run across some 
questions that my System Programers Manual doesn't seem to answer. Maybe
someone can help me out. I should state up front that my system is considered
"homebrew" and does not have support from anyone but me.

My questions:

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.

My documentation gives precious little information about the register setup
on the entry into a driver's interrupt routine. Could someone enlighten me?
What is the purpose of the BITA #1 instruction that always seems to be at
the beginning of the routine?

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. By looking at
the system calls for getsta and setsta I have concluded that the most of
the setup and expected return values are passed directly/returned from the
driver, at least in the device ready case. Is there some better documentation
on these entry points? New documentation would likely explain when and how
the getsta entry should return the number of bytes available to be read.

Thanks to anyone who may be willing to venture an explanation.

Dave Lowe
hp-pcd!hpvcla!davel