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From: del@pilchuck.UUCP (Erik Lindberg)
Newsgroups: net.micro.pc
Subject: Re: Serial Ports & Clock for PC
Message-ID: <410@pilchuck.UUCP>
Date: Fri, 5-Sep-86 00:25:55 EDT
Article-I.D.: pilchuck.410
Posted: Fri Sep  5 00:25:55 1986
Date-Received: Sat, 6-Sep-86 00:01:54 EDT
References: <5100135@uiucdcsb>
Organization: Data I/O - FutureNet Corporation, Redmond, WA
Lines: 45
Summary: Supported, sort of

In article <5100135@uiucdcsb>, dollas@uiucdcsb.CS.UIUC.EDU writes:
> 
>    1) Is there any literature about a real-time clock for a PC? I have a

Check back issues of Byte, seems to me I saw one of their construction
projects for just such a beast. Sorry I can't be more specific.

>    2) This is partially related to question (1): Is it possible to add more
> serial or parallel ports to a PC than the ones mentioned above? If so, I could 
> get an I/O board, if I could use all of the RS-232 ports. From some diagrams 
> that I looked it seems that there will be contention for interrupts, and if it 
> was connected to other COM ports it could mess the device of these ports,

There are four COM ports provided for in the architecture of the PC. There are
three problems with using them: 
1) DOS only supports COM1 and COM2, so you have to write your own support
   for COM3 and COM4 if you use them.
2) Only two interrupt vectors were allocated, so you can only have two of 
   your serial drivers interrupt driven. DOS does not support interrupt
   driven I/O on *either* of the standard COM[1|2] ports, so that is not
   as much of a problem as you might first think! And if one of your
   applications is for a serial printer, or similar device, you don't
   need interrupts anyway (so put it on COM[1|2] and use that COM's
   interrupt vector for one of you alternate COM[3|4] ports.)
3) Not all serial boards allow addressing at the alternate COM[3|4] I/O.
   This is (unfortunately for you) more common on the multi-function
   boards to reduce circuitry and configuration options.

> say, a floppy or hard-disk. On the same topic, if I get a mouse which plugs in
> the bus, do I lose the use of a serial port? I suspect the answer is 'yes', 

I suppose it depends on which mouse you get, but the Microsoft Mouse and
LogiTech mouse are both independant of any serial ports in the system.


del (Erik Lindberg) aka Hugable


Hugs: One of the few good things in life that are still free.
-- 

del (Erik Lindberg) aka Hugable


Hugs: One of the few good things in life that are still free.