[SOLVED] How to manage JTAG Vcc (5v) and the target Vcc (3.3v)

[ChineseSeller]

I am trying to connect JTAG to MIPS 24Kc SoC which has 8 pin out of the board. The pins are- TRST, TCK, GND, TMS, TDI, VCC, TDO, RST. My JTAG device is FTDI2332 based, 20 pin, ARM-USB-OCD from Olimex. The router's onboard Vcc pin (jtag) is 3.3v when JTAG debugger's Vcc is 5v. Unlike the 20 pin JTAG configuration, there is no Vcc (ref) pin onboard. Should I connect board's Vcc to the JTAG device's Vref pin (pin 2)? Or the Vcc pin remains floating on both sides?

 

[FvM]

Whatever you do, the JTAG levels must be reduced to 3.3V. Usually this would be achieved without level converters by supplying the FT2232 VCIO with 3.3 V.