dollas@uiucdcsb.CS.UIUC.EDU (09/02/86)
As these are my last days at the University of Illinois and I don't know
how soon I will have access to this net, I have a few questions:
1) Is there any literature about a real-time clock for a PC? I have a
PC's Limited machine (with which I am very happy), with plenty of ports
(2 serial, 1 parallel, light pen), and so I don't need the fancy I/O cards,
and $60 for d-Clock seems too high. Moreover, I intend to start 'augmenting'
the hardware of my machine and this is a good little project to start.
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,
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',
which means that an RS232 mouse may actually be preferrable. Is there any
software that allows for daisychaining of RS232 ports in a way that they are
all usable?
Anwers with e-mail are fine, as it will be forwarded to me. Thanks in
advance.
-Apostolos Dollas
For a few more days at:
USENET: ...!{pur-ee,ihnp4}!uiucdcs!dollas
CSNET: dollas@uiuc.csnet
ARPA: dollas@b.cs.uiuc.edudel@pilchuck.UUCP (Erik Lindberg) (09/05/86)
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.