JTAG HS3 TCK functionality

[SteveA]

Hi,

First of all I'd like to say that I'm new to Digilent and its products. I am in the process of assessing the JTAG HS3's suitability for an application and have a few questions which will hopefully help this process.

We wish to exercise a JTAG interface of a device located on a board whose scan chain and register architecture is known but non-standard. We are therefore looking at using the JTAG HS3 together with the Adept software and Adept SDK to drive data into and sample data from this device. The connector matches pin-for-pin the connector on our board which is great start! The user programmable TCK clock frequency nature of the HS3 is important here as TCK is (rather unusually) also used to derive the clock for the device's internal functional circuitry and we need that clock frequency to be around 6MHz. Can you please confirm whether the JTAG HS3 is able to be configured such that this clock (TCK) is continuous, i.e. running all the time even whilst there are no JTAG transactions taking place.

Thanks in advance,

SteveA

[JColvin]

Hi SteveA,

I have asked some of our applications engineers about this; they will get back to you here on the Forum.

Thanks,
JColvin

[malexander]

Hi SteveA,

While the JTAG-HS3 does support a 6 MHz TCK frequency it does not support continuous clocking of the TCK pin.

Thanks,
Michael

[D@n]

Have you thought about using the PMod output from one FPGA as a JTAG controller input for another?  You could certainly get a TCK value as controlled in frequency as you wanted to make it.  It would require a touch of soldering, and a touch of protocol writing ...

Yours,

Dan

[JColvin]

Tacking on to what Dan said, there is actually a Pmod that converts from the Pmod header style to JTAG style, the PmodLVLSHFT.

[SteveA]

Hi Guys, sorry for the delay in replying to all your helpful comments - thanks for all your replies. That's clear then - it doesn't support continuous clock which is a shame but a deal breaker for us. I'm looking at the PMod stuff to see what that offers - I wasn't aware of that product range so thanks for the heads up on that.

Regards,

Steve