d5kwedb@hacke9.dtek.chalmers.se. (Kristian Wedberg) (07/13/89)
I've written a Videotex program (Prestel type) for the Amiga, a kind of communication program. Trouble is, here in Sweden some folks have 75/1200 modems instead of the more normal 1200/1200. As it is, I have no idea how to support 75/1200, or indeed, if it's at all possible. Altzo, is it possible to transmit 75 bit/s and receive 1200 bit/s over the serial port? At the same time? Or would you need some kind of transformer? wonders kitte d5kwedb@dtek.chalmers.se
gert@targon.UUCP (Gert Kanis) (07/14/89)
In article <539@vice2utc.chalmers.se> d5kwedb@hacke9.dtek.chalmers.se (Kristian Wedberg) writes: >I've written a Videotex program (Prestel type) for the Amiga, a kind of >communication program. Trouble is, here in Sweden some folks have 75/1200 > >As it is, I have no idea how to support 75/1200, or indeed, if it's at all >possible. Problem you will have is that the rs232 port of the Amiga can only be set to 100 baud (bits per sec. probably this time) as the LOWEST speed! (It one of the little things the Amiga designers forgot :=) ) If you use a 75/1200 modem with an interspeeder the modem would take care of the speed conversion. However those modems are much more expensive. > >Altzo, is it possible to transmit 75 bit/s and receive 1200 bit/s over >the serial port? At the same time? > > wonders kitte d5kwedb@dtek.chalmers.se usualy in such cases (software) switching has to be done when changing from receiving to sending and vice versa. +-----------------------------------------------------------------+ | The smoker you drink,| Gert Kanis, SWP | | the W.C. | Nixdorf Computer BV, Postbus 29 | |----------------------| 4130 EA Vianen, Netherlands. | | I do not represent | E-mail : targon!gert@nluug.nl | | anyone elses opinion.| or ..!mcvax!targon!gert | +-----------------------------------------------------------------+
ckp@grebyn.com (Checkpoint Technologies) (07/15/89)
In article <539@vice2utc.chalmers.se> d5kwedb@hacke9.dtek.chalmers.se (Kristian Wedberg) writes: >I've written a Videotex program (Prestel type) for the Amiga, a kind of >communication program. Trouble is, here in Sweden some folks have 75/1200 >modems instead of the more normal 1200/1200. > >As it is, I have no idea how to support 75/1200, or indeed, if it's at all >possible. > >Altzo, is it possible to transmit 75 bit/s and receive 1200 bit/s over >the serial port? At the same time? Or would you need some kind of transformer? > First of all, the Amiga's serial port bottoms out at 112 baud. It's not possible to run it any slower. Secondly, the Amiga serial port does not allow split baud rates, that is, running transmit and receive at different speeds. The serial chip we use on our dual port serial card allows both the 75 baud speed, and split rate operation, though the driver we've written does not support split baud rates; and it plugs into a Zorro slot, and I imagine you're really talking about the A500. It's not possible to bang the bits on the Amiga serial port manually, so I don't know how to solve your problem, sorry. -- First comes the logo: C H E C K P O I N T T E C H N O L O G I E S / / \\ / / Then, the disclaimer: All expressed opinions are, indeed, factual. \ / o Now for the witty part: I'm pink, therefore, I'm spam! \/
marten@kuling.UUCP (M}rten Norman) (07/16/89)
From article <539@vice2utc.chalmers.se>, by d5kwedb@hacke9.dtek.chalmers.se. (Kristian Wedberg): > > Altzo, is it possible to transmit 75 bit/s and receive 1200 bit/s over > the serial port? At the same time? Or would you need some kind of transformer? As 1200/75=16 it _should_ be possible, if you are willing to fiddle with the hardware registers. Just send 16 "1200-speed-bits" to represent a "75-bit". The Hardware serial output register should agree with this, but i _dont_ think it's supported in standard software :-) --- M}rten Norman EMAIL: marten@kuling.uucp
kodiak@amiga.UUCP (Robert R. Burns) (07/18/89)
In article <539@vice2utc.chalmers.se> d5kwedb@hacke9.dtek.chalmers.se (Kristian Wedberg) writes: )... is it possible to transmit 75 bit/s and receive 1200 bit/s Use the serial port itself to receive 1200 baud. Wire up the transmit to some other Amiga output and generate it yourself -- 75 baud is slow enough to get right even with the latency noticing CIA time events. Note that this is a comp.sys.amiga.tech reply: it requires some programming expertise on your part :-) - Kodiak -- Bob Burns, amiga!kodiak _ | /_ _|. _ | Commodore __ |_) _ |_ _ )' |<(_)(_)|(_\|< /\ | ||| _` /\ |_)(_\| )(_\ | | \ Software ___/..\|\/|||__|/..\___ Faith
jms@tardis.Tymnet.COM (Joe Smith) (07/18/89)
In article <1052@kuling.UUCP> marten@kuling.UUCP (M}rten Norman) writes: >As 1200/75=16 it _should_ be possible, if you are willing to fiddle with the >hardware registers. Just send 16 "1200-speed-bits" to represent a "75-bit". >The Hardware serial output register should agree with this, but i _dont_ >think it's supported in standard software :-) When you send 8 bits to an async line, the hardware sends 10 bits by adding a start bit and a stop bit. Although one byte at 75 baud takes the same amount of time to transmit as 16 bytes at 1200 baud (160 bit times total), you can only specify 128 of the 160 bits. The remaining 32 bits will screw up the receiver at the far end. -- Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com McDonnell Douglas FSCO | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms PO Box 49019, MS-D21 | PDP-10 support: My car's license plate is "POPJ P," San Jose, CA 95161-9019 | narrator.device: "I didn't say that, my Amiga did!"
ecarroll@csvax1.cs.tcd.ie (Eddy Carroll) (07/21/89)
In article <539@vice2utc.chalmers.se>, d5kwedb@hacke9.dtek.chalmers.se. (Kristian Wedberg) writes: > I've written a Videotex program (Prestel type) for the Amiga, a kind of > communication program. Trouble is, here in Sweden some folks have 75/1200 > modems instead of the more normal 1200/1200. > > As it is, I have no idea how to support 75/1200, or indeed, if it's at all > possible. > > Altzo, is it possible to transmit 75 bit/s and receive 1200 bit/s over > the serial port? At the same time? Or would you need some kind of transformer? > > wonders kitte d5kwedb@dtek.chalmers.se Hi there, You will find it exceedingly difficult, if not impossible, to support 75/1200 directly on the Amiga, because the Amiga does not support split baud rates. 1200/75 on the other hand (as might be offered by a comms package) is much easier. I wrote a routine to do just that (i.e. send at 75 baud, receive at 1200 baud) for use with the Compunet Terminal software (Compunet is a Commodore/Atari Quantum-Link type system in the UK), to allow people to use the cheap "dumb" modems available in the UK to access Compunet. It works by expanding each character to be sent at 75 baud into 16 characters which are transmitted at 1200 baud, the 16 characters being chosen to produce as close a copy as possible of the desired 75 baud signal. It works pretty well, and it doesn't need to access the serial hardware directly (unlike some other methods I've seen). It should also work with any other computer that can send consecutive bytes over the serial line with no delay. I have a 12K file describing the theory, and giving example C code to show how it's used. I'm about to mail it to you, but if anyone else is interested (the reason for this reply) send me some mail to get a copy. -- Eddy -- Eddy Carroll ----* Genuine MUD Wizard | "You haven't lived until INTER: ecarroll@cs.tcd.ie | you've died in MUD!" UUCP: {..uunet}!mcvax!ukc!cs.tcd.ie!csvax1!ecarroll | -- Richard Bartle
d5kwedb@hacke9.dtek.chalmers.se. (Kristian Wedberg) (07/22/89)
Thanks for all replies to my question! There is no consensus wether 75/1200baud
on the Amiga is possible, but I will outline the major ideas:
1. NO, it's not possible.
2. Well, no, but if you use the serial port for receiving and hook up
transmitting to some other port on the Amiga doing the 75-baud part,
it should work fine.
3. Use a 75/1200 modem with 1200/1200 buffering. [Ok, so you loose the part
about it being cheap, but it does work...]
4. Try just what you said: software; when transmitting, send 16 MARK-bits or
16 SPACE-bits for every real bit you want to send. Stop-bits MIGHT foul
this up, but there you are...
5. By-pass the serial.device to get rid of start/stop-bits, then as in 4.
6. As in 4, but I know, it will work like a charm!
Well, I will defenitely try the last three. First, though, I must get my hands
on one of these modems, but it shouldn't be too hard, since there are quite
a few of them here in Sweden. Again, thanks!
kitte d5kwedb@dtek.chalmers.se
PS
I lost a letter from somebody in Canada asking about the mentioned videotex-
program. If you'll just mail me again, I'll get back to you.marten@kuling.UUCP (M}rten Norman) (07/25/89)
From article <431@tardis.Tymnet.COM>, by jms@tardis.Tymnet.COM (Joe Smith): > In article <1052@kuling.UUCP> marten@kuling.UUCP (M}rten Norman) writes: >>As 1200/75=16 it _should_ be possible, if you are willing to fiddle with the >>hardware registers. Just send 16 "1200-speed-bits" to represent a "75-bit". >>The Hardware serial output register should agree with this, but i _dont_ >>think it's supported in standard software :-) > > When you send 8 bits to an async line, the hardware sends 10 bits by > adding a start bit and a stop bit. Although one byte at 75 baud takes > the same amount of time to transmit as 16 bytes at 1200 baud (160 bit times > total), you can only specify 128 of the 160 bits. The remaining 32 bits > will screw up the receiver at the far end. > You are _so_ right! I overlooked the START/STOP-bit "feature"... Think I _should_ have done a double-check _before_ I launched some fake hope :-) --- M}rten Norman Email:marten@kuling.UUCP
doug@xdos.UUCP (Doug Merritt) (08/15/89)
In article <431@tardis.Tymnet.COM> jms@tardis.Tymnet.COM (Joe Smith) writes: >In article <1052@kuling.UUCP> marten@kuling.UUCP (M}rten Norman) writes: >When you send 8 bits to an async line, the hardware sends 10 bits by >adding a start bit and a stop bit. Although one byte at 75 baud takes >the same amount of time to transmit as 16 bytes at 1200 baud (160 bit times >total), you can only specify 128 of the 160 bits. The remaining 32 bits >will screw up the receiver at the far end. I would think there's a chance that they wouldn't screw it up, since we're basically talking about what would look like a glitch in 1/16th of the received waveform. Would depend on how the receiver hardware was designed, wouldn't it? Might still be worth a try. Doug -- Doug Merritt {pyramid,apple}!xdos!doug Member, Crusaders for a Better Tomorrow Professional Wildeyed Visionary