memory system question

Hi,
Wondering if any of you guys would be kind enough to help me.

Iam an Diagnostic apprentice engineer for quite a large Electronics manufacturer.

One of the senior engineers posed the following question.

'in a memory system, address lines 6&7 are s/c. A data patteren of 55 is written to address f080 and read back. What data would be read back and why??'

Perhaps the data on the two lines is added ???

And also how to test a full bank of memory,

Back gound info:

The prouducts that we work on a Computer motherboards from SunMicrosystems.

Your help would be greatly appreciated

Dom

 

[nbucska]

Shorting address bits won't change the data but
it will change the address i.e. the memory will see the same address when you address two different sets of locations.

If you short two logic lines, one driver will override
the other when the intended data are different so the address seen by the memory is not the same as the intended one. TTl-s generally can sink more current than source
For ECL it is just the opposite therefore -- when shorted --
TTLs behave as wired AND, ECL-s as wired ORs.

The result is that two sets of memory locations will have
the identical data -- the one which was written later.

To identify shorted address lines you write a sequence
of bytes into the whole memory and then read it back.
From the error pattern you can determine which bytes are
shorted or open.