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FT2232H JTAG TCK Clock Speed

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sagar:
Hi

I was trying to use FT2232H Channel A as JTAG and configured it. I have enabled JTAGHiSpeed API's from driver and disabled divide_by_5, to get 30MHz as TCK. But when I probe, I see 6MHz at TCK Pin.

1. Does FT2232H support 30MHz at JTAG-TCK?
2. Is it required for platform to provide 60MHz clock to FTDI or 12MHz crystal is sufficient? Or any other hardware change required?
3. Any reference driver/test to enable FT2232H JTAG TCK operating at 30MHz?

cioma:
I've been working with FT2232H a lot but I don't use FTDI drivers, instead I work directly through libusb.


--- Quote ---1. Does FT2232H support 30MHz at JTAG-TCK?
--- End quote ---

IIRC, yes, I think I measured it at some point.



--- Quote ---2. Is it required for platform to provide 60MHz clock to FTDI or 12MHz crystal is sufficient? Or any other hardware change required?
--- End quote ---

12 MHz crystal is sufficient, nothing else is needed in HW.



--- Quote ---3. Any reference driver/test to enable FT2232H JTAG TCK operating at 30MHz?
--- End quote ---

These are notes from my code:

Master clock is 60 MHz after /5 clock divider is disabled
required_clock = master_clock / (2 * (divider + 1))
divider = master_clock / required_clock / 2 - 1

If you set it to 30 MHz but actually measure 6 MHz then the /5 clock divider is enabled.

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