JTAG Configuration

Ivan,

The JTAG is powered from the 2.5V Vccaux.

Aust> Hi,

Oops, hit return too soon.

See page 554 of the User's Guide.

See note 1. Active pullup to Vccaux (2.5V)

Austin

Aust> Ivan,

All,

Hold that thought. The users guide is confusing (???).

In one section it states "open drain" and in another, it states "active pullup."

Will post as soon as I know,

Sorry for the confusion.

Austin

Ivan,

From the designers:

"VCCO_0 can be powered with 2.5V or 3.3V and the JTAG interface will work at that voltage. there is no need for any pull ups or supporting resistors on these pins.

the user's guide will be fixed because it is plainly misleading."

Thanks for finding this for us!

Aust> Hi,

Hi,

Anyone know what is Xilinx recommended pull-up resistor value for Virtex-4 configuration pins (TCK, TDO, TDI, TMS and M0-M2)?

Thanks, Ivan

Ivan,

If it is an output (e.g TDO), it is actively pulled up to Vcco_0.

If it is an input, use any reasonable value pullup resistor, and pull it up to the Vcco_0 supply (like 1K ohms, 10K ohms).

Aust> Hi,

Hi,

How about other input configuration pins that are not used in JTAG mode? Should I pull them up or down with 1/10K ohm resistor? Below is what I do, please let me know if this is okay.

CCLK_0 ? Pull down to GND with 1K ohm resister CS_B_0 ? Pull up to Vccaux with 1K ohm resistor (to disable SelectMAP data bus) D_IN_0 ? Pull down to GND with 1K ohm resister RDWR_B_0 ? Pull up to Vccaux with 1K ohm resistor (to set D[7:0] to outputs) VBATT_0 ? Pull down to GND with 1K ohm resister

PROGRAM_B_0 ? Pull up to Vccaux with 1K ohm resistor (No full-chip reset) PWRDWN_B_0 ? Pull up to Vccaux with 1K ohm resistor (No power down mode)

Thank in advance.

Thanks, Ivan