Query on schematic of CRII board

[Arvind Gupta]

Hi there,

 I am interested in a CRII board. As per the page 2 of schematic here, the 'JTAG/SPI programming header' connector has 200 ohms termination resistors and 10 K pull up resistors. Why so pls? Usually 50/75 ohm termination resistors are used. Also, why are pull up voltage resistors required for the two pins (namely TMS and TDI). I am supposing that this connector will connect the board with the PC.

Looking forward to your reply.

Thanks and Regards,

Arvind Gupta

 

[jpeyron]

Hi @Arvind Gupta,

We reached out to one of our design engineers and they responded that the 200 ohm resistors are protection against drive conflicts between an offboard programmer attached to header J8 and the onboard USB controller. The pull-ups are there so that the TMS and SS lines idle in the inactive states.

thank you,

Jon

[Arvind Gupta]

15 hours ago, jpeyron said:

Thanks for your reply. Can I ask what is J7 for  (in the same page 2).

Regards,

Arvind Gupta

[JColvin]

Hi @Arvind Gupta,

I believe that header just provides an alternate location to program the board. You'll note the data signals also tie in to the JTAG header J8.

Thanks,
JColvin

[Arvind Gupta]

14 hours ago, JColvin said:

Thanks for your reply. So as I understood there are two headers J7 and J8, both for programming the CPLD : one with 200 ohms resistances between itself and the CPLD (J8) as protection against drive conflicts between an offboard programmer & USB controller.and the other without the 200 ohm resistors (J7). It atleast does not sound logical to me . Since both are programing headers and share the same connections with the USB controller, both should have protection 200 ohms resistors in between itself and the JTAG pins. Can you kindly deliberate into the matter pls?

Thanking you again,

Arvind Gupta.

 

 

[JColvin]

Hi @Arvind Gupta,

I was informed that the Header J7 was used to program the USB controller as part of the manufacturing test for the CoolRunner II; it is not intended for customer use.

Thank you,
JColvin