Path: utzoo!utgpu!bnr-vpa!bruce
From: bruce@bnr-vpa.UUCP (Bruce Townsend)
Newsgroups: comp.sys.hp
Subject: GPIO (AFI) Interface Problem with HP9000s825 R2.0
Message-ID: <104@bnr-vpa.UUCP>
Date: 22 Nov 88 18:40:15 GMT
Organization: Bell-Northern Research, Ottawa, Ontario
Lines: 34

I am trying to use the gpio 16-bit parallel interface card on
the HP9000s825 (HP-UX rel 2.0), to continuously read or write
data at a rate controlled by the equipment connected to the
gpio card.  The data rate is clocked at 100K 16-bit words/sec,
and when a datum is presented to the gpio card, it must be read
before the next datum arrives, or it is lost.

 The problems I have encountered are:

1) The gpio will adequately read (or write) data at 100K words/sec,
   but only in 64K byte chunks.  When asked to read more, gaps of
   up to 20 msec occur, and so up to 2000 words are lost.  HP had
   promised that the aquisition rate would be maintained continuously,
   for a read to memory, limited only by the size of physical memory
   available.

2) Software interrupts do not interrupt a read or write on the gpio.
   As a single transaction can last many seconds (5M @ 100K/sec =
   50 seconds), the ability to interrupt in the middle is important.

3) Hardware interrupts do not seem to be supported.  Neither the EIR
   (external int. request) line not the two status lines (ST0, ST1),
   seem to be able to interrupt the gpio.

Is there anyone who knows about these deficiencies?  Are they being
addressed for Rel 3.0?  The HP9000s500 supported continuous reads of
up to 512K bytes, and both s/w and h/w interrupts were supported.
Hopefully the s825 can be made to work also.

regards,
-- 
Bruce Townsend (bnr-vpa!bruce)	Phone:	(613) 763-3008
Bell-Northern Research		Usenet: {utzoo, utcs}!bnr-vpa!bruce
P.O. Box 3511, Station C, Ottawa, Ontario, Canada, K1Y 4H7