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SSC Question [message #384414] Thu, 13 June 2019 05:09 Go to next message
Anonymous
Karma:
Originally posted by: Anthony Adverse

If you replaced the X-stal in the SuperSerialCard would it be feasible to achieve 38.4k? Even if you lost some of the other lower speeds? Or is the UART a limiting factor also?

A
Re: SSC Question [message #384417 is a reply to message #384414] Thu, 13 June 2019 13:40 Go to previous messageGo to next message
Michael J. Mahon is currently offline  Michael J. Mahon
Messages: 1767
Registered: October 2012
Karma: 0
Senior Member
Anthony Adverse <the.ertceps@gmail.com> wrote:
> If you replaced the X-stal in the SuperSerialCard would it be feasible to
> achieve 38.4k? Even if you lost some of the other lower speeds? Or is
> the UART a limiting factor also?
>
> A
>

Without any modification of the SSC, it can be configured in software to
provide 115k.

--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Re: SSC Question [message #384425 is a reply to message #384417] Thu, 13 June 2019 23:48 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: Anthony Adverse

> Without any modification of the SSC, it can be configured in software to
> provide 115k.
>
> --
> -michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com

That's intriguing, I always thought its max was 19.2k I guess the problem is nothing does it? I'll have to recheck proterm, I thought it only did 38.4 on a GS....

A
Re: SSC Question [message #384427 is a reply to message #384414] Fri, 14 June 2019 00:38 Go to previous messageGo to next message
Hugh Hood is currently offline  Hugh Hood
Messages: 678
Registered: November 2012
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Senior Member
Anthony,

The 'Turbo ASB' SSC daughtercard (by Lightning Systems) used a crystal
running at 2x the speed of the SSC crystal. It offered speeds up to
230,400 BPS, which, as Michael Mahon mentioned, is twice the 115,200 BPS
top speed of the stock SSC.

From the Reactive website:

< https://downloads.reactivemicro.com/Apple%20II%20Items/Hardw are/Turbo_ASB/Turbo%20ASB%20Manual.doc>


And, from an earlier post I made on the SSC/Turbo ASB difference:

>
> The 1.8432 MHz oscillator used by the SSC allows baud rates from 50
> BPS - 19,200 BPS (excluding 'high' speed mode).
>
> The 3.6864 MHz oscillator used in the Turbo ASB SSC daughtercard
> project allows those same rates times 2 (X2), with a top speed of
> 38,400 BPS in 'normal' mode, and a top speed of 230,400 BPS in 'high'
> speed mode. There are some DIP switches on that card that control the
> final frequency driving the ACIA.
>

So, you _could_ replace the crystal on the SSC and achieve 38,400 bps.
But, if you used the firmware, your speeds would be TWICE the stock
values. In any case, the 6551 will not be the limiting issue.

Consider, though, whether your IIe is fast enough to _receive data_ at
38,400 bps. The IIGS can do it, but I don't know about a 1 MHz IIe doing
it without the loss of characters.

FWIW, the last version of PT 3.1 (build date 1998) has drivers for the
Turbo ASB at the 38,400 bps speed. I suspect they would work with a SSC
board with a 3.6864 MHz oscillator in place of the stock one.

{Yes, I know that serial sultan David Schmidt does 115,200 bps both ways
with ADTPro, but that's because he's using a special protocol for bulk
(or is it batch, or packet?) transfers.}




Hugh Hood



On 6/13/2019 4:09 AM, Anthony Adverse wrote:
> If you replaced the X-stal in the SuperSerialCard would it be feasible to achieve 38.4k? Even if you lost some of the other lower speeds? Or is the UART a limiting factor also?
>
> A
>
Re: SSC Question [message #384432 is a reply to message #384427] Fri, 14 June 2019 07:39 Go to previous messageGo to next message
Anonymous
Karma:
Originally posted by: Anthony Adverse

> Consider, though, whether your IIe is fast enough to _receive data_ at
> 38,400 bps. The IIGS can do it, but I don't know about a 1 MHz IIe doing
> it without the loss of characters.
>
> FWIW, the last version of PT 3.1 (build date 1998) has drivers for the
> Turbo ASB at the 38,400 bps speed. I suspect they would work with a SSC
> board with a 3.6864 MHz oscillator in place of the stock one.
>
> {Yes, I know that serial sultan David Schmidt does 115,200 bps both ways
> with ADTPro, but that's because he's using a special protocol for bulk
> (or is it batch, or packet?) transfers.}
>
> Hugh Hood

I'm not sure if CloneE would keep up with 38.4 either, but at the moment my SSC is hiding out in my GS due to general onboard port weirdness :( Not looking for 115k I don't think the OrangePi or its serial adapter would cope with that too happily either.

I might have to see if I can find a substitute crystal at some stage. For what its worth the stock SSC driver in ProTerm only goes to 19.2k which is why I ask after being a little spoiled by the GS 38.4k

A
Re: SSC Question [message #384433 is a reply to message #384427] Fri, 14 June 2019 09:55 Go to previous message
David Schmidt is currently offline  David Schmidt
Messages: 993
Registered: October 2012
Karma: 0
Senior Member
On 6/14/19 12:38 AM, Hugh Hood wrote:
> [...]
> {Yes, I know that serial sultan David Schmidt does 115,200 bps both ways
> with ADTPro, but that's because he's using a special protocol for bulk
> (or is it batch, or packet?) transfers.}
> [...]

The trick with ADTPro is that it doesn't have to _display_ characters
that are coming and going at that rate. There's no way there's time for
that on a stock Apple II. But just moving characters out of the SSC and
into carefully aligned buffers works just fine. So in essence, yes, it
does batch transfers. It's an all-consuming task - there's hardly time
for anything else. And it doesn't use the firmware at all - there's no
time for that either. :-)
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