chamoun@lownlab.harvard.edu (Nassib Chamoun) (06/09/87)
On the 8088 PC the 8250 UART (serial port) uses a clock input of 1.8432 MHZ,
when divided by 16 will yield to the maximum transfer rate of 115,200 bits per
second. Can someone tell me if the 8250 on 286 and 386 machines uses higher
clock rates. If so will it allow for faster transfer rates. If not is
there a way of transferring data at higher serial rates ? any boards
available ? software or hardware gimmicks to alter 8250's input clock rate ?
Many thanks in advance.
NAME: Nassib G. Chamoun USPS: Lown Cardiovascular Laboratory
USENET: ...!harvard!lownlab!chamoun Harvard School of Public Health
PHONE: +1 617 732 1307 665 Huntington Avenue
Boston, MA 02115-9915markg@amdcad.AMD.COM (Mark Gorlinsky) (06/09/87)
chamoun@lownlab.harvard.edu (Nassib Chamoun) writes: > >On the 8088 PC the 8250 UART (serial port) uses a clock input of 1.8432 MHZ, >when divided by 16 will yield to the maximum transfer rate of 115,200 bits per >second. Can someone tell me if the 8250 on 286 and 386 machines uses higher >clock rates. The clock input to the 8250 comes from the crystal oscillator on the interface card. Normally this card will work in PCs as well as ATs, so the manufactures standarize on one design. Here's a little added info. The maximum operating frequency of the baud generator is 3.1 MHz. The fastest baud rate at that frequency is going to be 193,750 bps. -- Mark Gorlinsky - AMD Processor Products Division/APPS SQA UUCP: {ucbvax,decwrl,allegra}!amdcad!markg or amdcad!phil@decwrl.dec.com AT&T: (408) 982-7811 DISCLAIMER: What's mine is mine, not my employers.
davidsen@steinmetz.steinmetz.UUCP (William E. Davidsen Jr) (06/10/87)
In article <2247@husc6.UUCP> chamoun@lownlab.harvard.edu (Nassib Chamoun) writes:
:
:On the 8088 PC the 8250 UART (serial port) uses a clock input of 1.8432 MHZ,
:when divided by 16 will yield to the maximum transfer rate of 115,200 bits per
:second. Can someone tell me if the 8250 on 286 and 386 machines uses higher
:clock rates. If so will it allow for faster transfer rates. If not is
:there a way of transferring data at higher serial rates ? any boards
:available ? software or hardware gimmicks to alter 8250's input clock rate ?
As I recall, there is a field in one 8250 register which will allow you
to choose divide by 1, 16, or 64 (the last state is synchronous). You
could divide by 1, giving a max rate of 1.8432MHz, but I have no idea
what it buys you. Most of these parts don't like to run faster than
19.2kb.
NOTE: please don't send me your tale of how you run 115.2kb all the
time of 60 miles of abandoned railroad track... *most* 8250s don't run
reliably past 19.2kb, although you can probably go 76.8 with an error
correcting protocol and using 2 stop bits.
--
bill davidsen (wedu@ge-crd.arpa)
{chinet | philabs | sesimo}!steinmetz!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -me