When configuring a device in JTAG mode through the Parallel Cable III, how fast does the JTAG clock (TCK) oscillate?
The timing for this cable is controlled by the iMPACT configuration software. iMPACT drives the PC III TCK signal at 200-210 KHz and provides approximately 1.2 uS of setup time on the TDI and TMS signals.
Because all of the signals on the PC III cable are controlled directly through the software via the PC III driver, the timing is somewhat dependent on the clock speed of the computer running the Xilinx configuration software.
These numbers were measured using a Dell Latitude laptop with an 850 MHz Pentium-III processor.
The maximum TCK speed that is supported by the device being programmed is much higher than 200 KHz, but iMPACT limits the frequency to reduce the possibility of signal integrity problems.
For information on the Parallel Cable IV timing characteristics, please see (Xilinx Answer 14719).
For the maximum JTAG clock frequency supported by device architecture, please see (Xilinx Answer 8796).