Path: utzoo!mnetor!uunet!husc6!bbn!uwmcsd1!ig!jade!ucbvax!hoser.berkeley.edu!bryce
From: bryce@hoser.berkeley.edu (Bryce Nesbitt)
Newsgroups: comp.sys.amiga
Subject: WARNING: Upcomming changes to the serial.device !!!! (REPOST) !!!!
Message-ID: <22247@ucbvax.BERKELEY.EDU>
Date: 20 Dec 87 02:01:34 GMT
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: bryce@hoser.berkeley.edu (Bryce Nesbitt)
Organization: TVD
Lines: 103
Keywords: AmigaLine, Note #1
Summary: draft version of an in-progress multi-serial port standard.


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	  ***  AmigaLine, technical notes for Amiga programmers  ***
	  ***							 ***
	  ***	Currently unofficial, but I hope the Commodore	 ***
	  ***		  picks up on the idea. 		 ***
	  ***							 ***
	  ***  You are encouraged to anthologize and distribute  ***
	  ***	    these notes anywhere and everywhere.	 ***
	   ********************************************************

----------------------------------------------------------------------------
			Technical Note #1
      serial.device, warnings on multiple ports & future changes

SUMMARY

$ 1/0 serial.device, warnings on multiple ports & future changes
$ RFC (request for comment)
$ 19-Dec-87 Bryce Nesbitt / Infinity Software
$ devices, multiple ports, serial.device, PICs, interrupts, cards

    In the very near future extra serial port boards will be available for
    the Amiga.	For the benefit of everyone, the software should be ready
    in advance.  This note was prepared by the developers of the first
    (one of the first?) multi-port boards.


----------------------------------------------------------------------------

    We have taken great care to make the conversion to multiple ports
    nearly painless for everyone involved.


USERS

    The user will, at worst, need to drop an icon for the serial board into
    the "Expansion" directory.  At best the serial card will have
    AutoConfigure ROMs.

PROGRAMMERS

    Programmers must give the user the capability to select the unit number
    to open the serial.device with.  The built-in serial port will be unit
    0.	Additional serial ports will be numbered from 1 onward.  There is a
    hard limit of no more than 536,870,912 serial ports.

    Your OpenDevice() call will look something like this:

	error=OpenDevice("serial.device",unit,ioReqest,flags);

    That's really all there is to it.  Not too tough, eh?


HARDWARE DEVELOPERS

    Any manufacturer may add as many serial ports as they wish.  The drivers
    will register with a public port named "serial.port".  Your vectors
    will be placed in a newly-expanded table.  When a request is made to a
    function like BeginIO(), the IO_UNIT will be indexed off of a jump
    vector table.  From that point onward you have control.  Software latency
    does not get worse with additional ports.

    Form a hardware standpoint, all I need to say is "Interrupt Latency".
    Perhaps we can come up with support for direct user-interrupt vectors.
    For boards with lots of ports, a dedicated co-processor would be
    appropriate.


NOTES

    In the case were the user decides to switch units you must re-open the
    serial.device with the new unit information.  Don't forget to close the
    old unit.


    Some extra services will be available for the programmer.  This will
    probably include:

    * A Query to determine the number of serial ports.
    * A Query to determine the maxium baud rate of a unit.
    * A Query to determine the manufactuer and product number of a unit.
    * Timestamping for MIDI events.


    If the return from OpenDevice() is non-zero then the open failed.  This
    could be due to any number of causes:

    * The unit you specified does not exist.
    * The unit is set to exclusive access and is busy.
    * The serial.device could not be loaded.
    * The system is out of memory.

    Some of these errors will have new return codes.  This will be fleshed
    out fully in a future version of this tech note.  For now just inform
    the user of the failure to open the requested unit.

SEE ALSO

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