Intel BX80525KY500512 User Manual
Pentium
®
III Xeon™ Processor at 500 and 550 MHz
84
Datasheet
Due to the number of loads on the TCK signal, special care should be taken when routing this
signal on the baseboard. Poor routing can lead to multiple clocking of some agents on the debug
chain. This causes information to be lost through the chain and can result in bad commands being
issued to some agents on the chain.
signal on the baseboard. Poor routing can lead to multiple clocking of some agents on the debug
chain. This causes information to be lost through the chain and can result in bad commands being
issued to some agents on the chain.
The suggested routing scheme is to drive each agent's TCK signals individually from a buffer
device.
device.
III
Xeon processor system incorporating the Intel
®
450NX PCIset. A Bessel filter is recommended
over a series termination at the output of each buffer. The values shown in
are only
examples. The designer should determine the LC values appropriate for their particular application.
If it is desired to ship production systems without the 2.5V b uffers installed, then pull-up
resistors should be placed at the outputs to prevent TCK from floating
resistors should be placed at the outputs to prevent TCK from floating
An ITP buffer board drives the TCK signal through the debug port to the buffer device.
Figure 42. TCK with Individual Buffering Scheme
P0
P1
P2
P3
Debug Port
To each NX device, other
JTAG ...
TCK
2.5V Buffers
Pull up Resistor
2.5V
56 pF
56 pF
56 pF
56 pF
56 pF
56 pF
100 nH
100 nH
100 nH
100 nH
100 nH
100 nH