24 Apr
2010
24 Apr
'10
8:22 p.m.
I obtained an Intel SDK-85 eval board some time ago and decided to try
to bring it back to life today. It had been part of a Philips logic
analyzer demo system apparently. They had cut off the prototyping area
on the left side and put their own board there instead... which had a
2716 EPROM on it and some hardware to generate glitches as part of the
logic analyzer demo I guess.
In any case, I undid all of their mods (except of course, putting the
sawed off prototype section back on!) and the unit sort of works.
What I have discovered is that the 8355 ROM+IO chip is flakey. It won't
work unless I freeze it with component cooler. Once I have done that,
then it starts working and stays working for hours as long as power is
not removed. If it gets powered down, then I have to freeze it again
before the device will respond with valid fetches.
I don't suppose anyone has a spare 8355 with SDK-85 monitor burned in
it do they?
I'm guessing that's probably unobtainium so, failing that, wondering if
there's a .HEX of the ROM image floating around so that I don't have to
type it all in. If I have the bits, I can burn a 8755 that drops into
the same location.
Any guesses as to what the failure mode might be of the 8355? It is sort
of curious that once it gets started from frozen, it keeps working nicely.
I already did my time at ETA, cooling chips in liquid nitrogen so that's
kind of behind me now ;-)
Chris
--
Chris Elmquist
25 Apr
25 Apr
10:51 p.m.
On Apr 24, 2010, at 8:22 PM, Chris Elmquist wrote:
I obtained an Intel SDK-85 eval board some time ago
and decided to try
to bring it back to life today. It had been part of a Philips logic
analyzer demo system apparently. They had cut off the prototyping
area
on the left side and put their own board there instead... which had a
2716 EPROM on it and some hardware to generate glitches as part of the
logic analyzer demo I guess.
Neat!
In any case, I undid all of their mods (except of
course, putting the
sawed off prototype section back on!) and the unit sort of works.
Innnnteresting.
What I have discovered is that the 8355 ROM+IO chip is
flakey. It
won't
work unless I freeze it with component cooler. Once I have done that,
then it starts working and stays working for hours as long as power is
not removed. If it gets powered down, then I have to freeze it again
before the device will respond with valid fetches.
Bizarre.
I don't suppose anyone has a spare 8355 with
SDK-85 monitor burned in
it do they?
I'm guessing that's probably unobtainium so, failing that,
wondering if
there's a .HEX of the ROM image floating around so that I don't
have to
type it all in. If I have the bits, I can burn a 8755 that drops
into
the same location.
I have an SDK-85 handy; I'll see if my UniSite can read it when
configured for an 8755. I'll send you a hex file if I'm successful.
-Dave
--
Dave McGuire
Port Charlotte, FL
26 Apr
26 Apr
1:08 a.m.
On Apr 24, 2010, at 8:22 PM, Chris Elmquist wrote:
I'm guessing that's probably unobtainium so,
failing that,
wondering if
there's a .HEX of the ROM image floating around so that I don't
have to
type it all in. If I have the bits, I can burn a 8755 that drops
into
the same location.
Hmm, weird. I tried to read the ROM contents from the 8355 in my
SDK-85, but my Data I/O UniSite, when configured for an 8755A,
complains of a device insertion error. Everything is set up
properly, and the UniSite is fine, I use it all the time. I've
checked the databooks and the 8355 and the 8755 should be completely
interchangeable with the obvious exception of programmability.
I've not fired up this SDK-85 for a few years, but it worked fine
then. I have to go to sleep soon, and I'll be out for much of the
day tomorrow, but perhaps tomorrow night I'll be able to wire it up
to a power supply and see if it still runs.
-Dave
--
Dave McGuire
Port Charlotte, FL
7:45 a.m.
Thanks Dave! I appreciate the effort very much.
I'll check the datasheets too but there may be one pin that's different
on the 8355 from the 8755. On the SDK-85 board, there is a strapping
option to choose which device you are using and it messes with a +5 or
GND pull on one pin. Pin 5 seems vaguely familiar but I need to confirm.
So, there may be at least one difference between the two devices required
before you can fool the UniSite into reading the 8355.
Chris
On Monday (04/26/2010 at 01:08AM -0400), Dave McGuire wrote:
On Apr 24, 2010, at 8:22 PM, Chris Elmquist wrote:
--
Chris Elmquist
I'm guessing that's probably unobtainium
so, failing that, wondering if
there's a .HEX of the ROM image floating around so that I don't have to
type it all in. If I have the bits, I can burn a 8755 that drops
into
the same location.
Hmm, weird. I tried to read the ROM contents from the 8355 in my
SDK-85, but my Data I/O UniSite, when configured for an 8755A, complains
of a device insertion error. Everything is set up properly, and the
UniSite is fine, I use it all the time. I've checked the databooks and
the 8355 and the 8755 should be completely interchangeable with the
obvious exception of programmability.
I've not fired up this SDK-85 for a few years, but it worked fine
then. I have to go to sleep soon, and I'll be out for much of the day
tomorrow, but perhaps tomorrow night I'll be able to wire it up to a
power supply and see if it still runs.
-Dave
--
Dave McGuire
Port Charlotte, FL
9:53 a.m.
From: mcguire at neurotica.com
Subject: Re: i8355 from SDK-85 flakey
Date: Mon, 26 Apr 2010 01:08:11 -0400
To: cctalk at classiccmp.org; chrise at pobox.com
CC: cctech at classiccmp.org
On Apr 24, 2010, at 8:22 PM, Chris Elmquist wrote:
Hi
I don't have a data book handy but it seems that I recall that the
8355 can have a programmed inversion on one of the select lines.
There is also a difference between the 8755 and 8755A as I recall
as well.
Dwight
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I'm guessing that's probably unobtainium
so, failing that,
wondering if
there's a .HEX of the ROM image floating around so that I don't
have to
type it all in. If I have the bits, I can burn a 8755 that drops
into
the same location.
Hmm, weird. I tried to read the ROM contents from the 8355 in my
SDK-85, but my Data I/O UniSite, when configured for an 8755A,
complains of a device insertion error. Everything is set up
properly, and the UniSite is fine, I use it all the time. I've
checked the databooks and the 8355 and the 8755 should be completely
interchangeable with the obvious exception of programmability. 
9:21 a.m.
Hi Chris,
Freeze spray fixes usually give one additional troubleshooting information
but I've never seen a case where the component continues to work until power
is removed.
I suspect you are dealing with a reset, clock or timing issue as the
component powers up. Many Intel parts were very particular about their
signals on power-up so you might see if your timings and DC power ramps are
within specs.
Robo
-----Original Message-----
From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org]
On Behalf Of Chris Elmquist
Sent: Saturday, April 24, 2010 8:23 PM
To: Classic Computer Tech
Subject: i8355 from SDK-85 flakey
I obtained an Intel SDK-85 eval board some time ago and decided to try
to bring it back to life today. It had been part of a Philips logic
analyzer demo system apparently. They had cut off the prototyping area
on the left side and put their own board there instead... which had a
2716 EPROM on it and some hardware to generate glitches as part of the
logic analyzer demo I guess.
In any case, I undid all of their mods (except of course, putting the
sawed off prototype section back on!) and the unit sort of works.
What I have discovered is that the 8355 ROM+IO chip is flakey. It won't
work unless I freeze it with component cooler. Once I have done that,
then it starts working and stays working for hours as long as power is
not removed. If it gets powered down, then I have to freeze it again
before the device will respond with valid fetches.
I don't suppose anyone has a spare 8355 with SDK-85 monitor burned in
it do they?
I'm guessing that's probably unobtainium so, failing that, wondering if
there's a .HEX of the ROM image floating around so that I don't have to
type it all in. If I have the bits, I can burn a 8755 that drops into
the same location.
Any guesses as to what the failure mode might be of the 8355? It is sort
of curious that once it gets started from frozen, it keeps working nicely.
I already did my time at ETA, cooling chips in liquid nitrogen so that's
kind of behind me now ;-)
Chris
--
Chris Elmquist
28 Apr
28 Apr
7:54 p.m.
On Behalf Of Chris Elmquist
What I have discovered is that the 8355 ROM+IO chip is flakey. It won't
work unless I freeze it with component cooler. Once I have done that,
then it starts working and stays working for hours as long as power is
not removed. If it gets powered down, then I have to freeze it again
before the device will respond with valid fetches.
...
Any guesses as to what the failure mode might be of
the 8355? It is sort
of curious that once it gets started from frozen, it keeps working nicely.
I already did my time at ETA, cooling chips in liquid nitrogen so that's
kind of behind me now ;-)
robo351 wrote:
Hi Chris,
Freeze spray fixes usually give one additional troubleshooting information
but I've never seen a case where the component continues to work until power
is removed.
By way of anecdote, an early Nixie digital multimeter I used to use once
developed a problem: it would be working fine one moment, then, intermittently,
as one was making a measurement it would decide to go into a hard all-zeroes
display. Nothing would bring it out of that state except for powering it off
and back on. Very frustrating to use; struggled for ages (years) ans several
attempts to figure out what the trigger/fault was. Difficult to diagnose as the
various feedback loops in the discrete A/D converter made it impossible to
discern where the problem had initiated once it had been triggerred into the
fixed state. Of course, when one accessed the unit to work on it, it worked
fine and refused to fail at all.
As it turned out, a junction-FET had developed a sensitivity to changes in the
nearby electrostatic or electromagnetic field, or to stray photons: the
"+"-polarity indicator in the display was a neon lamp located within a few
millimetres of the FET, when the lamp switched on the FET would trigger into a
latch-up state. (Accessing the unit for service moved the neon lamp a couple of
centimetres away from the FET, which explained why it didn't fail then.)
So, all in the realm of speculation, but marginal or spurious semiconductor
junctions can do funny things, like exhibiting weird latch-up behaviour.
29 Apr
29 Apr
11:49 a.m.
On Wednesday (04/28/2010 at 04:54PM -0700), Brent Hilpert wrote:
As it turned out, a junction-FET had developed a sensitivity to changes in the
nearby electrostatic or electromagnetic field, or to stray photons: the
"+"-polarity indicator in the display was a neon lamp located within a few
millimetres of the FET, when the lamp switched on the FET would trigger into a
latch-up state. (Accessing the unit for service moved the neon lamp a couple of
centimetres away from the FET, which explained why it didn't fail then.)
Wow. Cool and crazy frusterating :-)
So, all in the realm of speculation, but marginal or
spurious semiconductor
junctions can do funny things, like exhibiting weird latch-up behaviour.
Indeed. Once I get the SDK85 back running like it should, perhaps
I'll poke around on the 8355 a bit and see if I can't find some clues.
I don't really have tools to do any serious analysis but I can do things
like vary the supply voltage, clock rate, etc-- a number of external
things-- and see if there are any margins over which it will work again.
Chris
--
Chris Elmquist
26 Apr
26 Apr
1:31 p.m.
I obtained an Intel SDK-85 eval board some time ago and decided to try
to bring it back to life today. It had been part of a Philips logic
analyzer demo system apparently. They had cut off the prototyping area
on the left side and put their own board there instead... which had a
2716 EPROM on it and some hardware to generate glitches as part of the
logic analyzer demo I guess.
In any case, I undid all of their mods (except of course, putting the
sawed off prototype section back on!) and the unit sort of works.
What I have discovered is that the 8355 ROM+IO chip is flakey. It won't
work unless I freeze it with component cooler. Once I have done that,
then it starts working and stays working for hours as long as power is
not removed. If it gets powered down, then I have to freeze it again
before the device will respond with valid fetches.
I don't suppose anyone has a spare 8355 with SDK-85 monitor burned in
it do they?
Alas not. But if the device works if you cool it, can't you read it out
when it's been cooled? Surely the SDK-85 has some kind of I/O port
you could dump it to. And then burn the bits into an 8755 as you suggested.
-tony
4:52 p.m.
On Monday (04/26/2010 at 06:31PM +0100), Tony Duell wrote:
Yes indeed. That will be plan B if Dave is unable to read his 8355 in
his PROM programmer.
The tty interface on this SDK-85 was built for 20mA current loop so I'll
have to either rework that to RS232 or invent a new method to offload.
But not a big deal really.
I'm thinking now that it might be nice to have the monitor source typed in
so maybe I will take on that challenge. I've yet to encounter a method
of scanning and OCRing dot-matrix printouts that works so I think that
just leaves typing it in.
Chris
--
Chris Elmquist
I don't suppose anyone has a spare 8355 with SDK-85 monitor burned in
it do they?
Alas not. But if the device works if you cool it, can't you read it out
when it's been cooled? Surely the SDK-85 has some kind of I/O port
you could dump it to. And then burn the bits into an 8755 as you suggested. 
7:01 p.m.
On Mon, Apr 26, 2010 at 1:52 PM, Chris Elmquist <chrise at pobox.com> wrote:
Yes indeed. ?That will be plan B if Dave is unable to read his 8355 in
his PROM programmer.
I'm thinking now that it might be nice to have the monitor source typed in
so maybe I will take on that challenge. ?I've yet to encounter a method
of scanning and OCRing dot-matrix printouts that works so I think that
just leaves typing it in.
I was able to dump the 8355 and reprogram it into an 8755 for an
SDK-85 I have. I should be able to send you a dump for that later
today if someone else doesn't beat me to it.
For the HP 5036A monitor what I did there to create an accurate
monitor listing without completely starting from scratch was to feed
the monitor dump into a special purpose disassembler I wrote and then
typed in all of the comments from the printed listing. That took a
while to finish and verify for correctness. This was the result:
http://www.decodesystems.com/5036ASM.TXT
Might not be too bad to repeat that process with the SDK-85 monitor.
27 Apr
27 Apr
9:58 a.m.
On Mon, Apr 26, 2010 at 4:01 PM, Glen Slick <glen.slick at gmail.com> wrote:
I was able to dump the 8355 and reprogram it into an 8755 for an
SDK-85 I have. ?I should be able to send you a dump for that later
today if someone else doesn't beat me to it.
I sent Chris a binary dump of the 8355 from my SDK-85. I haven't
uploaded it anywhere yet. If anyone else needs a copy I could send it
to them, or upload it somewhere.
-Glen
5:34 p.m.
On Tuesday (04/27/2010 at 06:58AM -0700), Glen Slick wrote:
On Mon, Apr 26, 2010 at 4:01 PM, Glen Slick
<glen.slick at gmail.com> wrote:
Yes... Thanks again Glen. I haven't gotten back to the project but will
soon.
And Tony, you are correct on the serial interface. It is sourced by the
SOD pin of the 8085 and then a single transistor drives the current loop.
You need to invert this before feeding into a 1488 or equiv RS232
driver but that's no big deal. All the TTY I/O runs at 110 baud,
timed by busy loops in the firmware but that's not a problem either.
There's a routine in the ROM called "co" which will bit-bang chars out
the interface as well as one called "nmout" which outputs ascii-hex bytes.
But, since Glen sent me the ROM image, I'm set with the bits. Now just
need to burn an 8755.
Thanks again for the help guys.
Chris
--
Chris Elmquist
I was able to dump the 8355 and reprogram it into an 8755 for an
SDK-85 I have. ?I should be able to send you a dump for that later
today if someone else doesn't beat me to it.
I sent Chris a binary dump of the 8355 from my SDK-85. I haven't
uploaded it anywhere yet. If anyone else needs a copy I could send it
to them, or upload it somewhere.
28 Apr
28 Apr
2:46 p.m.
And Tony, you are correct on the serial interface. It is sourced by the
SOD pin of the 8085 and then a single transistor drives the current loop.
It was Allison who said it used the SID and SOD pins of the 8085. However
this agrees wit hthe schematic in the book I have.
I can't find the links that Allison mentioned to seleect TTL/current
loop/RS232 mode. So either there are 2 versions of the board or my
scheamtics are 'simplified'. The only lionk I can see selects whether SID
comes from the current loop interface or is held low. If I am reading the
monitor lisitng correctly, then the bit of code starting at 0x0049 checks
to see if the SID pin is high or low. If the former it assumes a working
current loop device is connected (idle state would be to have the Tx loop
complete. so Q1 would be turned on, so SID high) and runs the teletype
monitor, if the latter, it runs the keypad/7-seg display monitor.
It's possible I've totally mis-uderstood this, I am not really a
programmer, and I've only just started looking at the SDK-85 monitor
source listings.
You need to invert this before feeding into a 1488 or
equiv RS232
driver but that's no big deal. All the TTY I/O runs at 110 baud,
I suspect you could use the current loop output trransistor as this
inverter (see my previous message). And I suspect that if you buffered
the RS232 output from you PC (using, say, a 1489), and fed that into the
current loop input -- pin 12 of J7 -- and cut R1 :-) then that would work
too. Or invert the output of the 1489 (say using a '04 -- or even another
secion of the 1489 as a kludge :-)) and feed it into the SID pin of the
8085 with the link S25 totally removed.
I would think that 110 bard would be trivial to do, and for the amount of
data you need to transfer, not a real problem. The monitor is 2K, 110
bard is 10 characters/second, so that's just oaver 200 seconds. Under 4
minutes.
timed by busy loops in the firmware but that's not
a problem either.
There's a routine in the ROM called "co" which will bit-bang chars out
the interface as well as one called "nmout" which outputs ascii-hex bytes=
Or you could run the tty monitor and use the 'D' command to dump the
approrpatie area of memory (0 to 7FF I think). Capture the incoming data
on the PC (I think any reasonable terminal progam can do that -- C-Kermit
certainly can) and write a simple program to decode the hex dump back to
binary.
-tony
27 Apr
27 Apr
2:37 p.m.
On Monday (04/26/2010 at 06:31PM +0100), Tony Duell wrote:
Yes indeed. That will be plan B if Dave is unable to read his 8355 in
his PROM programmer.
The tty interface on this SDK-85 was built for 20mA current loop so I'll
have to either rework that to RS232 or invent a new method to offload.
But not a big deal really.
I would be _very_ supprised if that serial interface doesn't sue some
TTL-level serial chip (or bit-banged through a TTL level port) followed
by a current loop interface.
In which case, since you need output only, grab the TTL leve signal at
the input to the coverter and feed it into something like a MAX232 (or a
1488 if you have +/-12V suppleis around).
-tony
I don't suppose anyone has a spare 8355 with SDK-85 monitor burned in
it do they?
Alas not. But if the device works if you cool it, can't you read it out
when it's been cooled? Surely the SDK-85 has some kind of I/O port
you could dump it to. And then burn the bits into an 8755 as you suggested. 
3:14 p.m.
Tony Duell wrote:
It does not. The DSK85 does bit bang through the SID and SOD pins
on the 8085 CPU.
On Monday
(04/26/2010 at 06:31PM +0100), Tony Duell wrote:
Yes indeed. That will be plan B if Dave is unable to read his 8355 in
his PROM programmer.
The tty interface on this SDK-85 was built for 20mA current loop so I'll
have to either rework that to RS232 or invent a new method to offload.
But not a big deal really.
I would be _very_ supprised if that serial interface doesn't sue some
TTL-level serial chip (or bit-banged through a TTL level port) followed
by a current loop interface.
I
don't suppose anyone has a spare 8355 with SDK-85 monitor burned in
it do they?
Alas not. But if the device works if you cool it, can't you read it
out
when it's been cooled? Surely the SDK-85 has some kind of I/O port
you could dump it to. And then burn the bits into an 8755 as you suggested.
In which case, since you need output only, grab the
TTL leve signal at
the input to the coverter and feed it into something like a MAX232 (or a
1488 if you have +/-12V suppleis around).
No need. The SDK can be via jumpers wired with run RS232 levels
for terminal. A minus 5 to 12 Volt supply is required but we are
talking a few milliamps.
The intel i8085 manuals had the schematic for the SDK85.
Allison
-tony
3:43 p.m.
The tty interface on this SDK-85 was built for 20mA
current loop so I'll
have to either rework that to RS232 or invent a new method to offload.
But not a big deal really.
I would be _very_ supprised if that serial interface doesn't sue some
TTL-level serial chip (or bit-banged through a TTL level port) followed
by a current loop interface.
In which case, since you need output only, grab
the TTL leve signal at
the input to the coverter and feed it into something like a MAX232 (or a
1488 if you have +/-12V suppleis around).
No need. The SDK can be via jumpers wired with run RS232 levels
for terminal. A minus 5 to 12 Volt supply is required but we are
talking a few milliamps.
The intel i8085 manuals had the schematic for the SDK85.
So does the book I've just pulled off my bookshelf ('Microcomputer
Theory and Applications wit hteh Intel SDK-85'). I can't find any links
to set RS232 levels on the serial port. The current loop converter is a
simple trasistor stage (PNP transsitor), emiter to +5V, collector to the
current loop through a resistor. Now, IIRC, the current loop passes
current in the idle state (whcih implies that transistor is turned on in
the idle state), but the RS232 signal is -ve in the idel state. So you
need an inverter.
I wonder (and I've not got an SDK85 to try it with). If you connected a
suitalbe pull-down resistor (say 1k) between the current loop +ve output
(pin 13 of J7 on my schematic) and ground, and then also connected pin 13
of J7 to the input of an RS232 driver, would that work? I think so.
Incidnetlaly, the book also has the monitor source lisitng in it. I don't
feel like typing it in, though :-)
-tony
6:18 p.m.
Tony Duell wrote:
It does not. The DSK85 does bit bang through the SID and SOD pins
on the 8085 CPU.
I would argue that is 'bit banged throug ha TTL level port'. The fact
that that port happens to be on the processor chip doesn't alter the fact
that tehre's a TTL level serial signal you can use.
Yes, but the SDK85 design you could jumper the IO for
RS232, 20ma or TTL.
If all else fails I suspect a common 'PP3' (as we used to call them) 9V
battery would do the trick.
It would or a common 9V wall wart.
I have that too. The inverter can be jumpered out.
Used a lot of SDK85s over the years with terminals
and it was never an issue. Wish I'd kept one but I do
have a home brew(wire wrapped) copy of one.
The tty
interface on this SDK-85 was built for 20mA current loop so I'll
have to either rework that to RS232 or invent a new method to offload.
But not a big deal really.
I would be _very_ supprised if that serial interface doesn't sue some
TTL-level serial chip (or bit-banged through a TTL level port) followed
by a current loop interface.
In which case, since you need output only, grab the
TTL leve signal at
the input to the coverter and feed it into something like a MAX232 (or a
1488 if you have +/-12V suppleis around).
No need. The SDK can be via jumpers wired with run RS232 levels
for terminal. A minus 5 to 12 Volt supply is required but we are
talking a few milliamps.
The intel
i8085 manuals had the schematic for the SDK85.
So does the book I've just pulled off my bookshelf ('Microcomputer
Theory and Applications wit hteh Intel SDK-85'). I can't find any links
to set RS232 levels on the serial port. The current loop converter is a
simple trasistor stage (PNP transsitor), emiter to +5V, collector to the
current loop through a resistor. Now, IIRC, the current loop passes
current in the idle state (whcih implies that transistor is turned on in
the idle state), but the RS232 signal is -ve in the idel state. So you
need an inverter.
I wonder (and I've not got an SDK85 to try it
with). If you connected a
suitalbe pull-down resistor (say 1k) between the current loop +ve output
(pin 13 of J7 on my schematic) and ground, and then also connected pin 13
of J7 to the input of an RS232 driver, would that work? I think so.
Again, there are jumper options for that.
Allison
Incidnetlaly, the book also has the monitor source
lisitng in it. I don't
feel like typing it in, though :-)
-tony
28 Apr
28 Apr
2:51 p.m.
Yes, but the SDK85 design you could jumper the IO for
RS232, 20ma or TTL.
OK, I am being dense... The schematics I have (which I will admit is
printed in a book, it's not an Intel original, but it does say
'Reproduced by permission of Intel Corporation') doesn't appear to show
any such links. It just shows 1-transistor buffer stages connected to the
SID and SOD pins.
Can you point me at a schematic of the SDK85 that does show these
jumpers, please.
-tony
4:51 p.m.
Hi
I was thinking about the problem that it would work after
freeze spray, until powered on again.
It might be that the failing bit was only used during boot
and not needed for the normal monitor operation.
This would then fail on the next reboot.
Just some idle thinking.
Dwight
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29 Apr
29 Apr
11:44 a.m.
On Wednesday (04/28/2010 at 01:51PM -0700), dwight elvey wrote:
Hi
I was thinking about the problem that it would work after
freeze spray, until powered on again.
It might be that the failing bit was only used during boot
and not needed for the normal monitor operation.
This would then fail on the next reboot.
Just some idle thinking.
Yes... that makes good sense Dwight. Some marginal bits in the
initialization code or some such. Scoping the bus does seem to indicate
that it is more software related... ie, I am not seeing weird levels
or signs that outputs are driving outputs or unable to drive full swing.
It just seems to run a little and then stop when it is not frozen.
Chris
--
Chris Elmquist
2:12 p.m.
Hi
I was thinking about the problem that it would work after
freeze spray=2C until powered on again.
That sounds quite likely. There's a routine that's only run on a cold
start which detects if there's a termninal connected and runs the
appropriate monitor.
It might be that the failing bit was only used during
boot
and not needed for the normal monitor operation.
This would then fail on the next reboot.
Just some idle thinking.
According to my schematic, there's space for 2 8355/8755 chips on the
SDK85 board. One is programmed with the monitor, the other is for
expansion (and is normally not fitted. If the OP gets a working 8755
containing the monitor, then it would be interesting to put the flakey
one in the expansion socket and try reading it out when cold and warm.
-tony
28 Apr
28 Apr
5:41 p.m.
On Wednesday (04/28/2010 at 07:51PM +0100), Tony Duell wrote:
I agree with you Tony. I have the original schematics that were included
with the board (and printed on 11x17 sheets), they match the schematics
in the manual for the board, and do not show any RS232 option. There is
a section in the book that shows how to wire up a 1488 and 1489 to build
such a converter but there is no place on the SDK85 board to do that.
They use one of the 1489 receivers as an inverter before driving the
TxD out one of the 1488 transmitters.
Anyway, probably beating a dead horse against a brick wall now as I
have verified the .bin file that Glen sent matches the listing in the
manual byte for byte so I have the bits I need. A couple 8755A are
in the mail and when I get those, will be good to go.
Thanks for the help.
Chris
--
Chris Elmquist
Yes, but the
SDK85 design you could jumper the IO for
RS232, 20ma or TTL.
OK, I am being dense... The schematics I have (which I will admit is
printed in a book, it's not an Intel original, but it does say
'Reproduced by permission of Intel Corporation') doesn't appear to show
any such links. It just shows 1-transistor buffer stages connected to the
SID and SOD pins.
Can you point me at a schematic of the SDK85 that does show these
jumpers, please.
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ajp166＠verizon.net -
ard＠p850ug1.demon.co.uk -
chrise＠pobox.com -
dkelvey＠hotmail.com -
glen.slick＠gmail.com -
hilpert＠cs.ubc.ca -
mcguire＠neurotica.com -
robo351＠verizon.net