Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

HSMC loopback adapter makes JTAG unusable

Hello, I am trying to use an HSMC loopback adapter on my Cyclone V SoC dev kit to debug it with SignalTap over the integrated USB Blaster. Each time I connect the HSMC loopback adapter, I can...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

The switch must be in "bypass" position when nothing is connected to HSMC.

I also see that the HSMC JTAG lines are not isolated by the multiplexer.

So the problem might be that the loopback adapter is shorting a JTAG line. Or it does not short it but the capacitive load compromises the signal integrity.

There should be no problems with the original loopback adapeter. It connects TDI to TDO, JTAG should even work in HSMC bypass or enable position.