Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/5/84; site kitty.UUCP Path: utzoo!watmath!sunybcs!kitty!larry From: larry@kitty.UUCP (Larry Lippman) Newsgroups: net.micro Subject: Re: Use of timers on INTEL 80186 Message-ID: <304@kitty.UUCP> Date: Sat, 10-Aug-85 19:06:00 EDT Article-I.D.: kitty.304 Posted: Sat Aug 10 19:06:00 1985 Date-Received: Sun, 11-Aug-85 08:27:24 EDT References: <542@brl-tgr.ARPA> <3437@utah-cs.UUCP> Organization: Recognition Research Corp., Clarence, NY Lines: 34 > We are building a small system here based on an INTEL 80186 > and are trying to use one of the on chip timers to generate a baud > rate clock. The '186 is running at 8 MHz (16 MHz crystal) and we > are trying to use TIMER 0 on the chip as the generator for a x16 > clock for a 9600 baud serial line. > Our processor registers (TIMER, DMA, memory control etc.) > are mapped to memory starting at F0000H. Our code does the > following: > Set location F0052H (Timer 0 A register) to 0DH > Set location F0056H (Timer 0 cntl) to C001H > The above is pretty much a copy of what is done in the INTEL > application note AP 186. It does work ONCE. It will continue to run > for hours this way but after the chip is warmed up if it is RESET or > powered down and back up again this timer won't work again. ... Simple problem, simple solution - I believe... Timer 0 and timer 1 both have INPUT pins (20 and 21, respectively) which ALWAYS do something. If you have EXT bit as 1, then these pins supply the external clock; if EXT is 0 and you are using the internal clock (as you are), then these pins function as a gate or reset depending upon the value of RTG bit. Since you have RTG as 0, and based upon your application, you must have pin 20 logically HIGH. I betcha it's floating in the breeze... One other piece of advice I have learned the hard way: Don't take the Intel APP notes as gospel! +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ | Larry Lippman @ Recognition Research Corp., Clarence, New York | | UUCP {decvax,dual,rocksanne,rocksvax,watmath}!sunybcs!kitty!larry | | {rice,shell}!baylor!/ | | VOICE 716/741-9185 syr!buf!/ | | TELEX {via WUI} 69-71461 ansbak: ELGECOMCLR | | | | "Have you hugged your cat today?" | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++