How to enable JTAG for BPI-R3

Hi,

I want to use the JTAG in BPI-R3. According to https://wiki.banana-pi.org/File:R3_gpio_40.jpg, I connect the pin 19,21, 23, 24 and one GRD pin 25 to the JTAG tool. Do I need to connect other pins?Seems these pins are multi-purpose pins.We also need to set some other settings. @sinovoip, would you help? Thanks!

Tony