JTAG interface - Clock does not seems like a clock

Hi,
what are you trying to achieve? USB Blaster or any other JTAG programmer isn't designed as a clock generator. It's sending JTAG commands and data to the connected JTAG chain and receiving responses. Nevertheless the behaviour can be explained:

The signal patterns you're seeing are related to different phases of JTAG communication.

1. Selecting a specific scan chain and operation mode in JTAG TAP controller using TCK and TMS lines.
2. Sending and receiving scan chain data using TCK, TDO and TDI lines.

To control all JTAG lines (Phase 1), USB Blaster is using kind of Bit banging commands, one step per USB data byte, respectively slow

Sending and receiving scan chain data is using special commands to exchange a burst of up to 63 Bytes at maximal supported speed of 6 MHz.

Happy developing
Frank