For more details about features and additional
description information on the device IEEE 1149.1 Standard–Test–Access Port, see the
corresponding sections within Signal
Descriptions and Detailed Description.
Note: The JTAG signals are split across two IO power domains on the
device. Timings parameters defined in this section only apply when the two IO power domains
are operating at the same voltage and level-shifters are not inserted into the signal path.
Values for the following timing parameters are not defined when operating the two IO power
domains at different voltages since propagation delay through the device IO buffers differ
when some are operating at 1.8 V while others are operating at 3.3 V. This effectively
reduces timing margin beyond the values defined in this section. The JTAG interface is still
expected to function when the two IO power domains are operated at different voltages,
assuming the system designer has implemented appropriate level-shifters and the operating
frequency is reduced to accommodate additional delay inserted by the level-shifters and IO
buffers operating at different voltages.
Table 7-94 JTAG Timing Conditions
PARAMETER |
MIN |
MAX |
UNIT |
Input
Conditions |
SRI |
Input slew rate |
0.50 |
2.00 |
V/ns |
Output
Conditions |
CL |
Output load capacitance |
5 |
15 |
pF |
PCB CONNECTIVITY
REQUIREMENTS |
td(Trace
Delay) |
Propagation delay of each
trace |
83.5 |
1000(1) |
ps |
td(Trace Mismatch
Delay) |
Propagation delay mismatch across all
traces |
|
100 |
ps |
(1) Maximum propagation delay associated with
the JTAG signal traces has a significant impact on maximum TCK operating frequency. It may
be possible to increase the trace delay beyond this value, but the operating frequency of
TCK must be reduced to account for the additional trace delay.