[Elphel-support] JTAG behaviour on 10359?

[Andrey Filippov]

> My first question is the Jtag on 10359. There exist a switch for share some
> wires. It is possible to program the FPGA with a normal JTAG adapter or do
> you use a special timing or protocol?
> I never used such special circuits in JTAG chains.
>

Hallo René,

Yes, you are right - some wires are multiplexed between JTAG and other
signals, because when developing that board (and
http://wiki.elphel.com/index.php?title=10347 that is used to control CCD
sensors and also has FPGA to be programmed) I was limited to the sensor
board interface signals. And I still had to add one line (it was GND in the
sensor interface) that goes to program pin on the FPGA. Multiplexer is
controlled by the FPGA itself, it has external pull-down resistor, FPGA
drives it high when programmed.

As for using "normal JTAG adapter" - unfortunately I can not help much as I
do not have such experience. I tried to design the cameras so our users do
not need to have any special devices to connect to the JTAG chains, all
required circuitry is built-in on the boards. User needs just a network
connector and GNU/Linux running on the host PC (installed system or just
running from Live DVD), no special JTAG adapters are needed to reprogram any
part of the camera.

Andrey
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