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Newsgroups: comp.sys.nsc.32k
Subject: Re: DUARTS etc
Message-ID: <9008311631.AA00800@halsoft>
Date: 31 Aug 90 16:31:52 GMT
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>[In the message entitled "Interrupt 15, RxRDY interrupts, and DUART device dri
vers.." on Aug 30, 20:01, John Connin writes:]
...
>> Also, could you generally comment on your design decision to provide
>> RxRDY interrupts.

>Ok, here's the scoop on RXrdy... UNIX has the nasty habit of disabling
>interrupts for extended periods of time, usually sitting at SPL5 or SPL6.
>Most serial drivers just live with this (since they run at SPL6 or
>below), and drop characters, unless you have nasty, expensive NS16550A's
>with FIFO's in them. I'm here to tell you that you don't need to put
>up with this anymore!
...					When a RXrdy interrupt occurs,
>the data is saved into a ring buffer (sized appropriately, not less than
>7 * 70 bytes per port: 512 bytes is a good number). At the end of the
>interrupt service routine, a TIMEOUT count is posted to an internal
>variable.

Looks like a pretty good scheme; but what's magic about 70 * 7 ( = 490 )
bytes for the buffer size?

PS.  I'm still looking for a Public Domain scanf().  Any hints on where
to find one?

Many Thanks:	

Jonathan Ryshpan		<...!uunet!hitachi!jon>

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