[Coco] deluxe rs232 pak / MPI

Tue Nov 24 21:09:49 EST 2009

On Tuesday 24 November 2009, Aaron Wolfe wrote:
>On Tue, Nov 24, 2009 at 7:30 PM, Gene Heskett <gene.heskett at verizon.net> 
wrote:
>> On Tuesday 24 November 2009, Aaron Wolfe wrote:
>>>Hi,
>>>
>>>I just acquired an rs232 pak and MPI.  The MPI seems to work fine with
>>>my coco 3, at least my drivewire rom pak works fine through it.
>>>I haven't been able to get the rs232 pak to work in basic or nitros9,
>>>with or without the MPI.  I have the original documentation from
>>>tandy, was wondering if things have changed for use in the coco 3.
>>>Also I have the 6309 instead of 6809, maybe this has some effect.  The
>>>MPI is 26-3024 "updated for use with the coco3".
>>>
>>>the docs say to do "EXEC &HC000" or "EXEC 49152" to access the setup
>>>routine in the pak's rom.  This results in various lockups on my coco
>>>3.
>>
>> The slot switch must be to the slot the pack is in at powerup unless the
>> MPI has been jumpered.  If it has been jumpered, then the packs eprom
>> should be pulled as there are other packs you may have plugged in that
>> will also have that as an exec address.
>
>hmm.  I can't get the EXEC to work even when the rs232 pak is directly
>connected to the CoCo, no MPI.  Could this mean a bad rs232 pak?
>
Good question.  Unforch I don't have a pat answer. I believe someone else 
answered with an exec &HE010 to put it back in the rom only mode first.

>I think I have to have the MPI's switch set to the slot my drivewire
>rompak is in so that the HDB DOS rom loads.
>Does this mean I cannot use the rs232 pak as the same time, or maybe
>this just means I must wire the IRQ lines together?
>
>>>looking through the nitros9 source I see that FF68 is base address for
>>>T2, and FF6C for T3.  Tried both with basically the same results.  I
>>>see there is a compiler flag for MPI usage, it is set.  I am not able
>>>to try nitros9 without the MPI because currently I must boot from
>>>drivewire  (really looking forward to that SD card pak, if you're
>>>listening Roger :).  the rs232 pak does not appear to have been opened
>>>for any modifications, label covering the screw was intact until I
>>>opened it just now to look for obvious bad components.
>>>
>>>when I "iniz /t2" or /t3, sometimes I get error 246, sometimes it
>>>works.  when it works, an irq routine shows up in the "irqs" command
>>>and the device is listed in "devs".  however, all attempts to pass
>>>data do not seem to work.  sometimes the coco locks up about the same
>>>time data is sent into the port, so I assume this means something
>>>somewhere is working, sort of?  might just be coincidence to be
>>>honest.
>>>
>>>should I put the rs232 pak in a specific slot of the MPI?
>>
>> I believe that most folks put it in the front slot, aka slot 1, byte
>> $FF7F=00.
>
>is there a setting in NitrOS-9 to tell it to set FF7F to 00?  Would
>this break the drivewire rompak in another slot?  (this rom is how I
>am booting nitros9)

Nitros9 normally maintains $FF7F at $33 in order to access the floppy 
controller in the back slot.  The convention for IRQ service routines is to 
read it, save it, and set it for the slot that this IRQ service routine is 
preset to access its hardware at.  And when the IRQ has been serviced, put 
the saved value back into $FF7F.

>>>do i need to wire all of the interrupt lines in the MPI together to
>>>make this work?
>>
>> Mine has been so wired for about 22 years, excellent idea if for no other
>> reason than all IRQ's _do_ get through to the cpu.  In your case, it
>> sounds like the IRQ from data rx'd may have gotten through, but the slot
>> switch, or the logic at $FF7F, is preventing the IRQ service routine from
>> accessing the pack, which in turn clears the IRQ, so you effectively have
>> an IRQ stuck on.

And I forgot that doing so also parallels all the pullup resistors, one for 
each slots pin 8, presenting the device attempting to pull down the IRQ line 
with perhaps more current to sink than it can do comfortably.  There are 4 
resistors along the front edge of the pcb in the MPI that are all alike, and 
may be as low as 2700 ohms each, I've seen 4700's and 2700's there.  It is 
safe to break out 3 of them, there by reducing the current the IRQ asserting 
transistor has to sink to do its job.

>>
>>>saw some posts about that.
>>>any tests I can do in basic, with the rs232 pak directly connected?  I
>>>
>>>saw a post about peeking values, they said:
>>>> ?PEEK(65384) usually reports 0 initially
>>>> ?PEEK(65385) usually reports 16 initially
>>>> ?PEEK(65386) and ?PEEK(65387) should report 0 initially
>>>
>>>the answer in the thread was that the user doing the troubleshooting got:
>>>
>>>
>>>?PEEK(65384) 0
>>>?PEEK(65385) 112
>>>?PEEK(65386) 0
>>>?PEEK(65387) 0
>>>
>>>I also get exactly these results, if that means anything.
>>>
>>>Basically I am not sure if the rs232 pak works, it was in storage for
>>>many years.  I am completely new to using an rs232 pak or an MPI, and
>>>actually new to OS-9 as well, so there are a huge number of unknowns
>>>here.  any hints or recommended practices are much appreciated. I'm
>>>not sure what tests to do to start eliminating possibilities.
>>
>> There is a possibility that the Aztec inverter supply in the pack has
>> gone to that great retirement pasture.  Since you have the MPI, you have
>> the plus and minus 12 volt supplies the chips need available in the mpi.
>>  You have to remove the Aztec assembly, and wire the cards edge connector
>> to feed those voltages in where the Aztec was feeding them.  ISTR I had
>> to superglue a couple of strips of thin copper plate into the blank
>> spaces to do that. PITA, but it works for me, and has been for at least a
>> decade.
>>
>> That rewired pack will NOT work in a coco3, as the coco3 has no -12 volt
>> line at all, and the load on the +12 line may be the straw that writes
>> fini to the coco3's power transformer if its not actively cooled.
>
>I guess that option is out, I am using a coco3.   But does that mean I
>could never use the rs232 pak on a coco3, since the coco3 have no -12v
>line?  sorry if I'm being dense.

If the aztec supply is pulled, then it can never be used in the coco3, only 
in the mpi.
>
>>>-Aaron
>>>
>>>--
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>>>Coco at maltedmedia.com
>>>http://five.pairlist.net/mailman/listinfo/coco
>>
>> --
>> Cheers, Gene
>> "There are four boxes to be used in defense of liberty:
>>  soap, ballot, jury, and ammo. Please use in that order."
>> -Ed Howdershelt (Author)
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>>
>> Oh don't the days seem lank and long
>>        When all goes right and none goes wrong,
>> And isn't your life extremely flat
>>        With nothing whatever to grumble at!
>>
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>
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>

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
The NRA is offering FREE Associate memberships to anyone who wants them.
<https://www.nrahq.org/nrabonus/accept-membership.asp>

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