Analog Devices HPPCI, Руководство пользователя

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JTAG Frequency Selection
1-8 HPUSB, USB, and HPPCI Emulators User’s Guide

Refer to Vi+ online Help for information about the
Vi+ Configurator and the ICE Test utility.
JTAG Frequency Selection
High-Performance PCI-ICE and High-Performance USB-ICE emulators
support a JTAG clock operation up to 50 MHz. USB-ICE emulators
support a JTAG clock operation of 10 MHz.
There is a relationship between the JTAG frequency and the core clock
frequency of the processor. Typically, the core clock runs at a frequency
that is more than 2x the JTAG clock’s frequency. On newer Analog
Devices processors, the core clock is a variable that is sometimes set by
switches or by software.

If the core/JTAG clock relation is not followed, scan failures may
prevent the emulator from connecting to the processor.
Choosing the JTAG Frequency Selection from the Settings menu in
Vi+ opens the JTAG Frequency Selection dialog box shown in
Figure 1-2 and Figure 1-3 . The dialog box is used to change the rate at
which the JTAG Test Clock signal (TCK) runs.
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Not all frequencies listed above appear for all processor families.
The displayed frequencies depend upon the processor family.
The tests listed in the Status box are run when you click the Test button
on the JTAG Frequency Selection dialog box. The blue arrow points to
the frequency currently being used. The arrow does not change after you
run the tests because pressing the
Cancel button goes back to using the
frequency pointed to by the blue arrow. To use a different frequency,
select the appropriate frequency from the list and click
Test . Clicking OK
uses the frequency that is highlighted and that has already been tested.
Table 1-1 lists and describes each of the available options.