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What on earth does "Command Over-run mean...?
- Thread starter highjon
- Start date
Hmmm my Hook (other similar 128x16 DMD game coincidentally also with Rottondog MPU) used to do this intermittently. It had other problems at the time, I *think* I cured it by normal practices, reseating connectors/ribbon each end on DMD, reseating display ROM, check power to DMD, check nothing closed on playfield. Lots of ideas in this Checkpoint thread but it never got fixed https://pinside.com/pinball/forum/topic/data-east-checkpoint-dmd-command-overrun-problem
Two things I'd check, measure the voltages arriving at the DMD connector, check R95 on back of DMD is in range, both described here;
http://techniek.flipperwinkel.nl/desega/index3.htm#dots
My machine has got more stable as I've improved the power side, re-capping the original power supply board (Checkpoint is getting on 30 years old!) and adding Inkochnito bridge board.
http://techniek.flipperwinkel.nl/desega/index3.htm#dots
My machine has got more stable as I've improved the power side, re-capping the original power supply board (Checkpoint is getting on 30 years old!) and adding Inkochnito bridge board.
With plain old standard (including rottendog) hardware, this is a bad connection between MPU and display board. Primary suspects are the connectors, and R95 as mentioned by astyy. It's a hard-working resistor so look up the band colour code and measure its resistance. If it doesn't match the bands, replace it. (Manual says it's a 33K 1/2 Watt resistor.) One of those rare cases where you do have a legitimate case to start looking at passives like resistors...
For the connectors, clean aggressively with solvent like IPA and try again. If there's corrosion on the pins, replace the connectors.
After both of these you will be 100% right as rain. If not then the machine's power supply is starting to go - that's the only remaining candidate and it's not my first suggestion as other effects would likely show up, as well.
Nothing wrong with the above mentioned general maintenance checks (e.g. reseating display ROMs) but that command overrun message has a specific meaning, and it is a breakdown in signal timings between MPU and display board - on these machines the MPU and the display board have separate CPUs working independently, and this is the display's CPU telling you that it's getting crappy inconsistent messaging from the MPU. If the game works in the slightest (proving that the MPU is sane) then the only candidate is the copper between MPU and display board.
(Just for entertainment's sake, it's worth mentioning that the MPU in these Data East/Sega games will usually not boot on the bench unless the display board is connected and powered on - the MPU tries to send ROM version data for the display board to show, and it waits for the display board to give the go-ahead to send that info. Without the handshake the MPU will sit and do nothing useful. They're not like Bally/Williams games that will at least have a fair shake at running 'headless'.)
For the connectors, clean aggressively with solvent like IPA and try again. If there's corrosion on the pins, replace the connectors.
After both of these you will be 100% right as rain. If not then the machine's power supply is starting to go - that's the only remaining candidate and it's not my first suggestion as other effects would likely show up, as well.
Nothing wrong with the above mentioned general maintenance checks (e.g. reseating display ROMs) but that command overrun message has a specific meaning, and it is a breakdown in signal timings between MPU and display board - on these machines the MPU and the display board have separate CPUs working independently, and this is the display's CPU telling you that it's getting crappy inconsistent messaging from the MPU. If the game works in the slightest (proving that the MPU is sane) then the only candidate is the copper between MPU and display board.
(Just for entertainment's sake, it's worth mentioning that the MPU in these Data East/Sega games will usually not boot on the bench unless the display board is connected and powered on - the MPU tries to send ROM version data for the display board to show, and it waits for the display board to give the go-ahead to send that info. Without the handshake the MPU will sit and do nothing useful. They're not like Bally/Williams games that will at least have a fair shake at running 'headless'.)
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did you ever get this sorted out? i am having similar issues.
https://pinside.com/pinball/forum/topic/data-east-checkpoint-dmd-reset-issues
https://pinside.com/pinball/forum/topic/data-east-checkpoint-dmd-reset-issues
OP
OP
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- Jul 21, 2011
- Messages
- 250
I think re-seating all the connectors seemed to fix it, although I never got to the bottom of it..... good luck
More than likely that was simply the fix required. Corrosion on connectors leading to a less-than-solid signal... replacing them scrubbing off some of the oxidisation and making a better signal. Light corrosion sometimes just needs the connectors to scrape off the oxidation just by the mechanical action of connecting. It's the heavier stuff that needs a glass fibre pen, or replacement wholesale of the connectors.
