BUGGS@cup.portal.com (William Edward JuneJr) (05/28/89)
I've read recently about the Double Click serial port expansion box allowing the STs or Megas to operate to 38400 baud. Is this true? I definately want to know!!! I've been thinkin' of gettin' a USR dual standard(HST & V.32) modem for my BBS. It would be GREAT to do 14.?K transfers WITHOUT data compression!! I thought there were custom chips inside the STs that limit it to 19.2K?? Then you have to a version of TOS that supports flow control, AND software that utilizes this speed. Did I hear another vicious rumor or can this really be done? Ed June
whack@nmsu.edu (Warren J Hack) (05/29/89)
Newsgroups: comp.sys.atari.st
Well, here goes again...
The postings about the cartridge port spurned some questions of my own
with (maybe) some answers for everyone else. The E. Arthur Brown Co. is
selling two items for the ST cartridge port that I found intriguing.
The first is an adaptor for the port to convert it into a standard 44 pin
connector that will fit directly with the Radio Shack prototyping boards.
For $15, they suggest such uses as RAM disks and clock boards. The second
item is a 24 Bit I/O board for TTL level I/O that can be software configured
for either 24 bit individual I/O or 16 bit with 5 levels of interrupts.
Instructions come with it to tell how to use this to WRITE to the port.
For $50, this seems extremely intriguing.
My questions concern using these for supporting expansion cards. Could
these be used to support IBM-expansion boards such as VGA/EGA graphics or
to support a math coporcessor board, or something like that? I am not a
very computer technically oriented person and would appreciate any responses
about these ideas (feasibility, possibility, ...). If nothing else, this
gives those people looking for ways to use thier cartridge port an answer
on WRITING to it. Please e-mail me your repsonses and I will post the
collective repsonses.
Warren J. Hack
INTERNET: whack@nmsu.edu
BITNET: gast9042@nmsuvm1.BITNET
Disclaimer: I am not associated with E. Arthur Brown Co. or anyone else
(except my wife)...hyc@math.lsa.umich.edu (Howard Chu) (06/01/89)
In article <18870@cup.portal.com> BUGGS@cup.portal.com (William Edward JuneJr) writes: >I've read recently about the Double Click serial port expansion box allowing > the STs or Megas to operate to 38400 baud. Is this true? >I definately want to know!!! >I've been thinkin' of gettin' a USR dual standard(HST & V.32) modem for my BBS. >It would be GREAT to do 14.?K transfers WITHOUT data compression!! >I thought there were custom chips inside the STs that limit it to 19.2K?? >Then you have to a version of TOS that supports flow control, AND software > that utilizes this speed. >Did I hear another vicious rumor or can this really be done? > >Ed June It's easy. You need to call Rsconf to reset a bit in the UCR, then you need to reset the baud rate timer... Basically, when you use Rsconf to set the baud rate of the serial port, it always puts the UART in divide-by-4 mode. Reset that to divide-by-1, then you need to set the correct counter values in the timer (TImer D, is it? I've forgotten already. Sigh.) to get the baud rate you want. You can calculate them pretty easily, or, if you have the ST Internals book, you can find the ROM values in the BIOS listing. Multiply those by 4 for speeds in the usual range. Divide the value for 19.2 by 2 to get 38.4. It works. 61.4 can also work, but you can't do a lot of extra processing if you want to keep up. -- -=- PrayerMail: Send 100Mbits to holyghost@father.son[127.0.0.1] and You Too can have a Personal Electronic Relationship with God!
apratt@atari.UUCP (Allan Pratt) (06/02/89)
In article <665@stag.math.lsa.umich.edu>, hyc@math.lsa.umich.edu (Howard Chu) writes: > [38KBaud on an ST] > It's easy. You need to call Rsconf to reset a bit in the UCR, then you need > to reset the baud rate timer... Basically, when you use Rsconf to set the > baud rate of the serial port, it always puts the UART in divide-by-4 mode. > Reset that to divide-by-1, then you need to set the correct counter values > in the timer [yes, it's Timer D] to get the > baud rate you want. You can calculate them pretty easily... Actually, the UART is in divide-by-16 mode, not divide-by-4. Timer D is running as fast as it can; *that* is where the divide-by-4 comes in. If you change the bit in the UART to divide-by-1, you disable certain synchronization logic in the UART and reliability goes down the toilet. Talking to my VAX at 9600 with this trick, there is lots of noise. 19.2 is the pits, and I've hooked up two STs at 38 and it's unusable (too many glitches). If you can do it and are satisfied with the results, more power to you. Personally, I would consider leaving the UART at divide-by-16 so the synchronization logic works, and placing a different clock on the 68901's baud-rate inputs instead, but that involves finding a clock and running a jumper, and makes the baud rate nonprogrammable. (Just don't put a different clock on the 68901's CLOCK input, since that controls all the timers; there isn't a separate Timer D input.) ============================================ Opinions expressed above do not necessarily -- Allan Pratt, Atari Corp. reflect those of Atari Corp. or anyone else. ...ames!atari!apratt
uace0@uhnix2.uh.edu (Michael B. Vederman) (06/02/89)
The question is, how can the ST utilize 38400 baud, or is this a vicious rumor?
It is stated correctly that Double Click Software's DC-PORT RS232 Expansion
cartridge does allow this.
In another posting, Howard Chu suggests that the MFP in the ST can be set to
use a divide by 1 for Timer D (baud rate clock) to acheive faster rates. While
it is true that you can do this, and theoretically acheive higher rates, the
variance due to clock fluctuation makes using a divied by 1 would be extermely
unreliable.
DC-PORT has a uart on board that can handle baud rates that quickly, and since
i/o is acheived thru the cartridge, 38400 baud is an easily accomplished feat.
As a side note, anyone interested in purchasing a DC-PORT should note that we
are offering free DC-PORT cables until July 1 (a $30 value!) with the order of
each DC-PORT. We are also taking special orders for five port versions.
If you would like more info about DC-PORT, please e-mail me a message.
ALSO, Double Click Software's support BBS is running right now at 713-944-0108.
- mike
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