space invaders ram

baz

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ok i have armed myself with a logic probe.

im a lil lost , what is it im looking for to id a fault in a ram ic with a logic probe ?

do i test a certain pin to see if its a pulse , low or high ?

i just want to check my ram ics as im trouble shooting a board fault.
 
Not sure if you can definitively test any RAM chip with a logic probe. But I'd be looking for "activity" (i.e. not steady high or low) on the enable/select line(s), as well as all of the data lines. Should also be activity on some (but not necessarily all) of the address lines. Consult a datasheet for your particular RAM IC to identify which pin is which line. Note that lack of the expected activity may not indicate a fault with the RAM, but instead with the address decoding circuitry, or maybe something else jacking up the bus.

To actually "test" it, you'd need to either remove it and use some type of test equipment, or hook up a Fluke 9010 (or similar equipment) which can then test any device that's addressable.

Oh, and there's the Braze kit. It appears to have code which does some self-test/diagnostics on the hardware (which the original lacks): http://www.brasington.org/arcade/products/sim/selftest.shtml
 
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