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AR# 23385

8.2i ISE - Project Navigator lists inaccurate options for Virtex-5 Configuration Rate


Keywords: BPI, SPI, config, implementation, configuration, speed, master, clock, oscillator, frequency, Generate Programming File, options, BitGen

The configuration rate listed for the Virtex-5 device family is the same as that listed for all other FPGA device families. Is this correct?

The configuration selected does not seem to match the actual configuration rate coming from the chip.


ISE 8.2i lists the following possible frequencies for Virtex 8.2i Configuration Rate (in MHz):

4, 5, 7, 8, 9, 10, 13, 15, 20, 26, 30, 34, 41, 45, 51, 55, 60

Selecting one of these ConfigRate options will produce roughly twice the selected frequency from the hardware device. For example: Selecting 4 gives ~8Mhz on chip, selecting 5 gives ~10Mhz on chip, etc. Note that the published +/- 50% variation still applies.

In the first service pack for ISE 8.2i (8.2.01i) the possible frequencies for Virtex-5 Configuration Rate will be correctly changed to:

2, 6, 9, 13, 17, 20, 24, 27, 31, 35, 38, 42, 46, 49, 53, 56, 60

In ISE 8.2.01i, the selectable ConfigRate values will directly correspond to the Configuration Rate of the hardware device in MHz +/- 50%. For example: Selecting 2 gives ~2Mhz on chip.

This change in 8.2.01i is only for Virtex-5. All previous FPGA families remain with the original set of Configuration Rate frequencies.
AR# 23385
Date 04/16/2009
Status Archive
Type General Article