percom block PBTOOLS - A pair of utilities to manipulate a PERCOM block.

[_The Doctor__]

Funny as I read all of this, I heard the phrase 'You can't take it with you...'   strange inheritance is a show we watch.

It's a legacy in one form or another, each generation builds on the other.

 

In earnest, I want you to know that what I finalized my post with is exactly how so many feel.

[+DrVenkman]

Holy shit, everyone. This is supposed to be a hobby that people actually enjoy. The world is in rough enough shape currently and I doubt many of us come to AtariAge to get more of the same that we see in the news right now.

 

Thanks for the cool new utility, Thom, and thanks Jon and Konrad for all the rest of the software you have provided and continue to provide to the community. 

[drac030]

Perhaps tschak909 is right that I was missing the point, but I did not take this conversation as anything else than a conversation where we perhaps disagree (on the releasing the sources or not), but well, where it is said that everyone has always agree with everything...

[tschak909]

sorry, I started a row. My bad.

-Thom

 

[drac030]

Nothing to be sorry about, IMHO

[+Larry]

Some of you might be interested in this INSIGHT: Atari column from (the late) Bill Wilkinson:

https://www.atarimagazines.com/compute/issue65/insight_atari.php

 

This was my first introduction to the Percom Block.

-Larry

 

Edit: found a copy of Bill's BASIC program in my archives.  Pretty sure it is a type-in version, so treat it with caution if you play around with it.

 

Percom Block from Insight Atari.atr

[drac030]

Quote

 

5    1 Density (0=Single, 4=Double)

(...)

For the Density byte of the config block, I don't know of any drives which use values other than 0 (FM mode, single density) or 4 (MFM mode, double density). If you find a drive that actually uses some other value (not just ignores it), let me know.

 

 

I do not know such drives either, but, for some reason, the SDX Formatter, when you select 77 tracks, sets bit 1 in this byte, making it $02 for FM and $06 for MFM. And it has been doing so since ICD times, to be sure. So there may be a bit more to it.

Edited April 8, 2020 by drac030

[_The Doctor__]

|\O/|         

   |

  / \

 

8 inch drives, 3.5 inch drives  possibly... there were others as well, but certainly not the paper tape reader...

[E474]

Hi,

 

   I wouldn't mind a copy of the sources.

[phaeron]

13 hours ago, drac030 said:

 

I do not know such drives either, but, for some reason, the SDX Formatter, when you select 77 tracks, sets bit 1 in this byte, making it $02 for FM and $06 for MFM. And it has been doing so since ICD times, to be sure. So there may be a bit more to it.

The Percom RFD40-S1 and the ATR8000 switch to 8" mode when bit 1 is set, doubling the FDC clock speed and the bit rate.

[_The Doctor__]

Thanks for confirmation.

[drac030]

15 hours ago, phaeron said:

The Percom RFD40-S1 and the ATR8000 switch to 8" mode when bit 1 is set, doubling the FDC clock speed and the bit rate.

Does RFD40-S1 also respect the field which in the article quoted above is labelled "ACIA" and supposedly controls the transmission parameters on the drive's side? If so, how does it work?

[phaeron]

1 hour ago, drac030 said:

Does RFD40-S1 also respect the field which in the article quoted above is labelled "ACIA" and supposedly controls the transmission parameters on the drive's side? If so, how does it work?

This byte is not used in any Percom firmware that I have seen so far (RFD V1.00-1.20, AT-88, AT88-SPD V1.11-1.21), nor in the ATR8000. In Percom drives, the 12 byte block is directly mirrored from the firmware's internal DCB with no translation and little to no checking. In the RFD firmware, the last three bytes are simply uninitialized and unused, while AT-88 firmwares initialize byte 9 to $51 but still don't use it.

 

$51 is the configuration value used to initialize the 6850 ACIA. It corresponds to receive IRQs disabled, /RTS high, transmit IRQs disabled, 8 data bits + 2 stop bits, and /16 clock divider. However, all firmwares that I have seen hardcode this value in the initialization routine and don't read it from the DCB. There's very little that could be done with this value anyway as the 6850 transmit/receive clock is hardwired to 4MHz / 13 = 307KHz; the only lower divider is /1 and that is unusable with asynchronous transmission. Only the AT88-S1PD/SPD has high speed capability by switching to SIO CLOCK OUT as the external clock, which requires special setup on the computer side incompatible with US Doubler style high-speed and it isn't used by the firmware anyway.