Debug Port Design Guide for UP/DP Systems

DPDG for UP/DP Systems Order Number: 313373-001 21

XDP Design Guide

3.7 Observation Port Routing Guidelines

There are 4 observation ports on the XDP labeled A through D. Each observation port is

made up of 4 OBSData lines and 2 OBSFN control/strobe lines.

These lines in the past have had historical names associated with them. The OBS_Port

historically has been referred to as the BPM#[0:5] pins.

For reference: OBSFN_x0=BPM5#=PREQ#; OBSFN_x1=BPM4#=PRDY#;

OBSDATA_x3=BPM0#; OBSDATA_x2=BPM1#; OBSDATA_x1=BPM2#;

OBSDATA_x0=BPM3#

3.7.1 Observation Port Configurations

In a uniprocessor system, the OBS port signals must be routed only to Port A. In DP or

MP systems there is some flexibility with which device goes to which Observation Port.

Port A and B must have devices of a UP or DP scan chain. Port A and B must have

devices of scan chain 0. Port C and D must have devices of scan chain 1. However

within each pair of ports, there is no restriction on swapping. The same port may not

service two devices nor should you connect the same device to two ports.

This means that processor0 may be routed to either port A or B and CPU1 would be

routed to the remaining port. Clarification: UP systems may only route to port A.

3.7.2 Observation Port Routing

Terminations on these signals vary based on processor. Check the documentation on

the last device on each signal to see if it has on-die termination (ODT). If it does not,

the signal requires a 51 ohm pull-ups to VTAP. Note that no termination is needed on

the debug port side of the transmission lines.

3.7.3 OBSFN_x[1:0]

Run control operations involve the assertion of signals on processor pins BPM5# and

BPM4#.

Notes:

1. The traces marked ‘A’ must be length matched with other OBS signals

2. The trace lengths marked ‘A’ must not exceed 1.5ns and must be length matched to one another to within

50ps.

Figure 3-7. BPM[4:5] Routing

Processor

BPM4#

BPM5#

XDP

OBSFN_A1

OBSFN_A0

Vtt

51 ohm