NetNews Usenet Archive 1993 #3/NN_1993_3.iso/spool/comp/sys/mac/oop/macapp3/549

Internet Message Format | 1993-01-21 | 1.8 KB

Path: sparky!uunet!think.com!ames!data.nas.nasa.gov!taligent!apple!applelink.apple.com
From: [e-mail] (Biodex Corp, Keith Fieldhouse,PRT)
Newsgroups: comp.sys.mac.oop.macapp3
Subject: Serial Port Hardware Overrun?
Message-ID: <[e-mail]>
Date: 21 Jan 93 02:12:00 GMT
Sender: [e-mail]
Organization: AppleLink Gateway
Lines: 27



I am encountering a problem using the modem port within a MacApp aplication
that I'm working on.  I am communicating with a measurement device and most of
the data is going from the device to the Mac.  I process input from the Mac in
a ::DoIdle method in the event handler that manages the device for me.  In
general this works very well.  I've set the ports *software* buffer to a size
that essentially assures that I won't encounter software overruns while running
(input from the device only comes when asked for within the ::DoIdle).  I don't
encounter software overruns.  Occaisonally, however, I do encounter a hardware
overrun.  The serial connection is 96008N1 running on a Mac LCII.  Currently
there is no handshaking whatever between the devices. Quite frankly I'm
suprised that even a lowly LC II can't keep up with data in that configuration
but to be honest I have no basis for that belief -- other than the fact that
the vast majority of the time sees the connection working just fine.

My question is, what things (MacApp releated or not) affect the serial driver'
ability to keep up with the data connection?   I'm not opposed to putting in
hardware handshaking (I'd prefer not to use Xon/X0ff as that would complicate
data transmission) but I'd like to understand better just what is going on when
I get these hardware overflows.  Any light you can shed will be greatly
appreciated.

Regards,

Keith