jojo@speedy.WISC.EDU (Jon Wesener) (11/04/87)
Believe it or not, I need to make my serial port go 115K Baud! I saw code to do this once, but I'm not sure where, If anyone has any ideas, examples, CODE! which does this, please send me mail!!!! I know you have to muck with the 8250, literally teach it how to do it by dropping several different types of hardware checking, but I need specifics. Also, Is it possible, and I have reason to believe it is, to get data IN through the parallel ports data lines. The tech refs shows one way arrows (going out) but I want the diagram to show arrows going both ways and it's not as easy as drawing them in on the diagram. (damn) thanx in advance, --j jon wesener jojo@speedy.wisc.edu "remember kids, just say NO! to MSDOS"
davidsen@steinmetz.steinmetz.UUCP (William E. Davidsen Jr) (11/05/87)
In article <4594@spool.wisc.edu> jojo@speedy.WISC.EDU (Jon Wesener) writes: | | Believe it or not, I need to make my serial port go 115K Baud! |I saw code to do this once, but I'm not sure where, If anyone has |any ideas, examples, CODE! which does this, please send me mail!!!! In the 8250 there are two divisor fields. On is a two bit field controlling divide clock by 64, 16, 1, or syncronous operation. There is also a 16bit counter quantity which is used to dicide down the clock (which has already been divided by 1,16, or 64). How to use it. The clock rate is 115200, so if you set the count to 1, you will operate at 115200 bps. There is no guarantee that this will work, since the chip is rated at most for 19200, but that's the way it's done. You may have to upgrade your 8250 with another (compatible) chip, I don't have the number handy, but I seem to recall Signetics and/or AMD (please help me some hardware guru). Note that all of the common baud rats are factors of 115200. The only two which don't come out exactly are 110 and 134.5, which are close enough to work in most cases anyway. I would have mailed this, but I think it may be of general interest. The details start on page 6 of the AT tech ref, volume 2. -- bill davidsen (wedu@ge-crd.arpa) {uunet | philabs | seismo}!steinmetz!crdos1!davidsen "Stupidity, like virtue, is its own reward" -me