Debug Port Design Guide for UP/DP Systems

DPDG for UP/DP Systems Order Number: 313373-001 27
XDP-SSA Design Guide
4 XDP-SSA Design Guide
4.1 Conventions
Special Note: TDI is an output of the debug port connector and TDO is an input of the
debug port connector despite their nomenclature. The opposite is true of a processor.
TDI is an input of a processor and TDO is an output.
4.2 XDP-SSA Routing Overview
The XDP-SSA (Second Side Attach) is a 31-pin alternative to the XDP for those
customers needing to place the debug port on the non-component side of the board. As
there are fewer pins, XDP-SSA has significantly fewer capabilities than XDP
Routing for the XDP-SSA is similar to the XDP. As such, the sections in this chapter will
make significant references to Section 3, “XDP Design Guide” on page 13 in this book.
This section contains a thumbnail sketch of how to connect all debug port signals,
except TDO/TDI, in the simplest connection configuration. Please refer to the details of
each signal for complete information. These drawings represent only the most basic
connection.
Note that any signal that is not noted on this drawing may be left as no connect.
4.3 JTAG Routing Guidelines
4.3.1 TDI - TDO Routing Guidelines
The XDP-SSA TDI-TDO routing guidelines are the same as those for the XDP0 TDI-TDO
(see Section 3.3.1, “TDI - TDO Routing Guidelines” on page 16).
Special Note: TDI is an output of the debug port connector and TDO is an input of the
debug port connector despite their nomenclature. The opposite is true of a processor.
TDI is an input of a processor and TDO is an output.
4.3.2 TCK0 Routing
The XDP-SSA TCK0 routing guidelines are the same as those for the XDP0 TCK0 (see
Section 3.3.2, “TCK0 Routing” on page 18).
Suggestion: As signal integrity of TCK is one of the primary sources of run control
failure, provide a scope test point at ALL device loads (processor, chipset, etc.). This
suggestion is typically implemented only on the first spin of a system.
4.3.2.1 TMS Routing Guidelines
The XDP-SSA TMS routing guidelines are the same as those for the XDP0 TMS (see
Section 3.3.3, “TMS Routing Guidelines” on page 18).
There is no trace length requirement for this signal.