To reiterate what Kev has touched on, often in the case of screen ram (and indeed rom). It is not desinged to be read, only written .
 
Take a Galaxian board.
 
The program only writes to the video ram. A completely independent set of logic based (not microprocessor controlled) hardware then reads this ram, accesses the object roms and dumps the contents to the screen. It never reads back what it's put on the screen. Hence, again to use Galaxian as an example, there are also two ROMs that you can't test using the Fluke because they are not within the space addressable by the processor.
 
One of the first mistakes i bumped into a few months ago :O)
 
Martin
-----Original Message-----
From: owner-techtoolslist@www.flippers.com [mailto:owner-techtoolslist@www.flippers.com] On Behalf Of James Bright
Sent: 09 October 2003 14:25
To: techtoolslist@www.flippers.com
Subject: Re: [techtoolslist] Frogger testing on Fluke 9010A

Couple quick suggestions (I have not looked at this board yet):
 
1) Are you able to Run UUT? I always try this to make sure that my pod works in the board. That is just a safety check.
2) Do you have a probe? With a probe you can confirm that you've mapped the right address to the right chip. What you can do is something (manual from the keypad) like:
 
  SYNC ADDRESS
  WRITE @ <suspected start address>
  LOOP
 
and then you can probe the 2114 at the chip enable pin to ensure that the chip you is indeed getting selected. In your case, I don't think it is.
 
Also 2114s (for one hi/lo 2114 pair), the test range will be something like 0000 - 03FF.
 
--James Bright
www.QuarterArcade.com
Restored Arcade Games for your Home
----- Original Message -----
From: pc2jamma
To: techtoolslist
Sent: Wednesday, October 08, 2003 10:09 PM
Subject: [techtoolslist] Frogger testing on Fluke 9010A

Hi guys !
 
 
I'm facing one problem that is driving me crazy !
 
I have one 9010A with Z80QT Pod, I'm testing one known good Frogger (Sega Gremlin) board. So far so good ! But "the problem is" : I have one 2114 sockted at position 50, and does not matter if I remove this IC or replace with a damage one, it passes on both short and long RAM Test... I also did the Quick Test and nope.
 
I'm testing the following addresses:
 
8000h-87FFh  Passes OK
A800h-ABFFh  Passes OK
AC00h-AFFFh  Passes OK
 
I think there is something wrong on addresses... but I don't know the right ones... According to James's website the addresses are Okay, instead of AC00h-AFFFh that is not listed on the website.
 
Some of you guys can help me on that please ?
 
 
Thank you very much !
 
 
Jos� Luiz Martins