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From: mandler@apollo.HP.COM (John Mandler)
Newsgroups: comp.sys.apollo
Subject: RE: use of parallel port on new 400t
Message-ID: <5011ee72.20b6d@apollo.HP.COM>
Date: 27 Feb 91 19:57:00 GMT
Sender: root@apollo.HP.COM
Reply-To: agq@itd1.dsto.oz
Organization: Hewlett-Packard Apollo Division - Chelmsford, MA
Lines: 64

< agq@itd1.dsto.oz (Ashley Quick) writes >


>> We have a few new 400t's here, - the ones with the build in
>> parallel port.
>> 
>> How does it work?

        The parallel port is a *standard* centronics port with bi-directional
        capabilities. The output data lines are active high; strobe and
        acknowledge are active low; busy, paper empty, and online are active high
        and fault is active low. The output protocol operates as follows :
            ws (workstation)  places data on lines, lowers strobe, and waits for busy 
            high from external device. 
            ws then rasies strobe, and waits for busy == false and 
            acknowledge pulse before begining next cycle. 

        Since not every device drives every status line, you must use the configuration
        file, pio1.conf, to tell the kernel which status lines are active and how
        to handle events on them. Best bet to hook up a new printer is to set
        all the status lines to ignore, then cat a file to the /dev/pio1. Once that
        works, you must read the printer manual to determine which status lines are
        active, and set them to either wait or fatal. 

        There are 2 handshake modes in the standard software, BNACK or BONLY. 
        Since sr10.3 we have discovered some printers do not raise busy in
        response to the leading edge of strobe. A patch will be available next month
        to support these devices. My guess is this is the solution to your
        problem.                         


>> 
>> Crazy thing is, some other people have a DATAPRODUCTS laser printer
>> hooked up with the config file containing utter rubbish - and theirs
>> works fine.
>> 
>> I beleive that DataProducts use a Parallel interface with most of the
>> control signals the inverse of Centronics. Is the 400t only capable
>> of driving the DataProducts mode?????                    

        I think you are confused. The Dataproducts  printer that connects
        to dsp80's and dn4/6xx machines uses an inverted dataproducts interface.
        This is nothing like the centronics interface, and will never work. 
        I suspect the laser printer you refer to works because the pio driver
        is using the default status and handshake settings which match this
        particular printer.
        


>> Furthermore, the type manager EXPLICITLY reads the config
>> file from "/sys/node_data/etc/pio1.conf" - this means that on
>> a 400t running diskless, the config file is stored in the
>> partners node_data directory, rather than the diskless nodes.
>> 
>> If the file was `node_data/etc/pio1.conf there would be no
>> problem.


        Good point. This will be fixed in sr10.4 . 

        John Mandler  mandler@apollo.hp.com
        Hewlett-Packard Company
        Chelmsford, MA
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