Testability
13 Testability
In the GMCH, testability for Automated Test Equipment (ATE) board level testing has
been implemented as an XOR chain. An XOR-tree is a chain of XOR gates each with
one input pin connected to it which allows for pad to ball to trace connection testing.
The XOR testing methodology is to boot the part using straps to enter XOR mode (A
description of the boot process follows). Once in XOR mode, all of the pins of an XOR
chain are driven to logic 1. This action will force the output of that XOR chain to either
a 1 if the number of the pins making up the chain is even and a 0 if the number of the
pins making up the chain is odd.
Once a valid output is detected on the XOR chain output, a walking 0 pattern is moved
from one end of the chain to the other. Every time the walking 0 is applied to a pin on
the chain, the output will toggle. If the output does not toggle, there is a disconnect
somewhere between die, package, and board and the system can be considered a
failure.
Datasheet
339
INTEL [ INTEL ]
