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Kyle22

19,200 on an 850 UltraSpeed Possible?

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I had a thought about the 850. It's a simple bit-banger, so what are the limits of the hardware? Is it possible to kick up the baud rate between the 850 and the computer to 38,400?

 

Even if this involved changing to a faster crystal, it would still be a great thing.

 

Ideas, Thoughts...?

 

 

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I had a thought about the 850. It's a simple bit-banger, so what are the limits of the hardware? Is it possible to kick up the baud rate between the 850 and the computer to 38,400?

Even if this involved changing to a faster crystal, it would still be a great thing.

 

 

The 850 hardware is very similar to the 1050. Same CPU at the same clock, same RIOT chip used for the data ports. There is technically no reason why the 850 couldn't bitbang as fast as the 1050 USD or a Happy 1050. One relevant issue is serial input that is asynchronous, a complication you don't have on the 1050. And concurrent I/O is normally transparent anyway (the module just mirrors the serial input into the SIO bus). But say, for something like printer output, it shouldn't be a problem.

Edited by ijor

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I just wish someone would come out with a new run of MIO type devices. (I have a 256k that I'm using and somewhere in storage I have a 1mb, both original ICD units).

 

But the CSS Black Box or something else would be great. Even a PBI "serial/parallel" (or even serial only) device.

 

Any of the "more technically endowed" able to speculate how fast of a serial port a PBI device could theoretically handle?

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I just wish someone would come out with a new run of MIO type devices. (I have a 256k that I'm using and somewhere in storage I have a 1mb, both original ICD units).

 

But the CSS Black Box or something else would be great. Even a PBI "serial/parallel" (or even serial only) device.

 

Any of the "more technically endowed" able to speculate how fast of a serial port a PBI device could theoretically handle?

 

http://www.rasterline.com/mio.html

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PoKey is capable of 100+K baud. The problem is RTS/CTS flow control. I have been wanting to expand on the R:Verter design to include a joystick port connection for flow control lines. That would be a cheap and universal interface.

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The 850 hardware is very similar to the 1050. Same CPU at the same clock, same RIOT chip used for the data ports. There is technically no reason why the 850 couldn't bitbang as fast as the 1050 USD or a Happy 1050. One relevant issue is serial input that is asynchronous, a complication you don't have on the 1050. And concurrent I/O is normally transparent anyway (the module just mirrors the serial input into the SIO bus). But say, for something like printer output, it shouldn't be a problem.

 

I'd be happy with 19,200, but even 38,400 is less than the ~52K that the USD can reliably do.

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That really won't help here. This is SIO we're working with. Thanks, though.

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I'd be happy with 19,200, but even 38,400 is less than the ~52K that the USD can reliably do.

 

As I said, hardware wise it shouldn't be a problem at all for the 850 to do the 52K USD. All you need is just a custom ROM, assuming there is enough space. But again, that won't work for serial input without some kind of redesign.

 

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I had a thought about the 850. It's a simple bit-banger, so what are the limits of the hardware? Is it possible to kick up the baud rate between the 850 and the computer to 38,400?

 

Probably not. For that, you need to know how the 850 works. If you enable the concurrent mode, then the serial speed is really up to Pokey. What the 850 does in this case is that it samples the input serial line, and mirrors the output, 1:1. It does this by polling the input line with the CPU, and simply placing the same signal at the output. Thus, the bitrate is limited by the (half the) highest frequency the 1Mhz CPU within the 850 can sample the data.

 

There is a good reason why the 850 is limited to 9600 baud. If you want higher serial speeds, a direct upconverter from +5V to +/-12V is probably the better choice, such as a pair of 1488 and 1489 chips. Problem is to get RTS/CTS hardware handshaking working.

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I guess I'm stuck with 9600 for now, but that's OK.

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Hello Kyle22,

 

Can you please explain what the use of the serial connection would be?

What is it supposed to acheive?

I'm trying to understand the significance of an endavour to create a fast serial device for the Atari.

 

BR/

 

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I am using it as a modem interface for a BBS. It is connected to a LANTronix UDS-10.

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Are the speeds on the P:R: Connection any better/faster? I have historically used a R-Verter but have a few PR's laying around....

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As far as I know, the P:R:C has the same limitations as the 850.

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According to the manual on Atarimania the ICD P:R: Connection is capable of 19,200, but they are fairly rare.

 

a8maestro at one time sold a 19.2k modified version of the R-VerterII, but I don't believe he still does. He is registered on AA but hasn't been logged in since last April.

 

I did find the following page from his site where information/schematics about the R-Verter I and II are available. The R-Verter II text file says it was capable of 19.2k, 38.4k was tested but had too many errors.

http://atari.a8maestro.com/info/8ball/ballho.htm

Edited by BillC

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Before SIO2PC existed I used a P:R: Connection / null modem cable / PC clone to transfer files back and forth via zmodem. 14.4k worked sort of, but there were just too many errors and retries that running at 9600 was actually faster in the long run. I wonder if I had used a shorter serial cable if I would have had different results.

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The R:Verter has no speed limit. It just lacks RTS/CTS so you can't go fast without buffer overruns. It should be simple to add a joystick cable and another level converter chip. Then, with proper R: handler software, we could have handshaking. Really, a full-blown RS-232 port.

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No, because they are already used. I don't remember exactly how they are used, but there are not enough control lines available on the SIO port. We need a few more for proper handshaking.

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The R-Verter II files from the link I mentioned in post#18 show connections to MOTOR and PROCEED, while the MAX232 shows connections to CD, DTR, RTS.

 

rverter2.jpg

 

Edited by BillC

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Yes, there is a discrepancy in the documentation. This has been the main thing that has been holding me back on this. I love the R:Verter. It is simple, and it's just a level converter. PoKey does it all, and it works. Simple is best, BUT, we need to make it just a little more complicated.

 

How about we add some more level converters so we can monitor and control RTS/CTS, DSR.DTR. CD, etc.

Let's attach these new i/o pins to a joystick port.

 

Write a handler that does buffering and RTS/CTS control, and that's the perfect example of minimalist design.

 

Edit: And it would do 19,200, 38,400 or better...

Edited by Kyle22
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