06-16-2016 08:44 AM
I am using Xilinx XC7V2000T, and I place a Voltage-Level Translator, which is TXB0108, between JTAG and FPGA.
Now the JTAG chain can't be identified.
Vivado showed as below:
open_hw_target [lindex [get_hw_targets -of_objects [get_hw_servers localhost]] 0]
INFO: [Labtoolstcl 44-466] Opening hw_target localhost:3121/xilinx_tcf/Digilent/210203369470A
ERROR: [Labtools 27-2269] No devices detected on target localhost/xilinx_tcf/Digilent/210203369470A.
Check cable connectivity and that the target board is powered up then
use the disconnect_hw_server and connect_hw_server to re-register this hardware target.
ERROR: [Common 17-39] 'open_hw_target' failed due to earlier errors.
Then I used oscilloscope to test JTGA's TDI TDO TCK and TMS, all is normal, but the output of TXB0108 is strange.
JTAG's TCK is
And the output of TXB0108 is as below:
I don't know why this happened.
06-16-2016 08:51 AM
@Anonymous Can you share the Schematic of this interface.
06-17-2016 01:49 AM
Your problem seems to come from the TXB0108. The datasheet from TI, P.15, indicates :
Any external pulldown or pullup resistors are recommended to be larger than 50k.
You have 10k pullup resistors on TMS and TCK (R92, R93).
Did you try to change these resistors for higher values?
Also, it's not very clear in the datasheet, but in the functional diagram channel 2 to 8 seems to share the same 'one shot' circuit for the bus direction. Can this be clarified from TI?
06-17-2016 03:10 AM
Additionally, verify your SI and the minimum pulse width. Overshoots and undershoots (violates absolute maximum ratings of TXB0108) look like bad impedance matching.
06-17-2016 03:38 AM
I have changed the resistors from 10K to 50K, and I also removed the resistor, nothing changed.
In addition, I think the detail of channel 2-7 is the same, so the datasheet only draws one diagram.
I didn't contact TI.
06-19-2016 10:50 PM
Yes, the output of TXB0108 is strange. Please check the below things