Chapter 1 11
Introduction
Utilities board
Teststation interface
The teststation can be a PA-RISC based workstation. The interface to
the teststation is an ethernet AUI port for flexibility in connecting to
many workstations. It is also easily expandable.
DC test of a node
To perform the DC test, the Test Bus Controller (TBC) first scans data
to all boards in a node. Then each JTAG device performs a capture step
that completes the movement of the test data from the driver to the
receiver. This step is described in the JTAG 1149.1 specification.
AC test of a node
To perform the AC test, the Test Bus Controller (TBC) scans data to all
boards in a node and then loads an AC test instruction into all ASICs
on one board at a time. The scan ring on each board is paused.
Once all boards have been loaded with the AC test instruction, the TBC
takes all boards out of pause mode simultaneously, causing them all to
exit update together and execute the AC test.
The AC test enables clocks inside the ASICs so that they test internal
and external paths at the system clock rate. They all execute on the same
system clock.
JTAG fanout
The teststation interface is thin ethernet. In addition to the teststation,
this port is also used for the console ethernet. There is one cable that
connects to all the nodes and to the teststation (if it exists) and to
whatever device or network that will display the console.
