> I have some JTAG connectors I do not know the pinout. > Does someone knows how to use xoscope to detect the JTAG pinout?
Target or adapter side? If you want to find out the pinout of connectors on a target, the best starting point is to look for datasheets of all the chips on the target; probably there are dedicated JTAG pins. Then try to measure connectivity between those pins and the connector. If you don't have a low-current continuity checker or ohm meter, you could instead inject a small AC signal at one of the device JTAG pins and try to locate it on the connector. It's not possible to differentiate the pins using only a scope unless you can actually watch some JTAG transfers. But as you don't know the pinout, you probably also can't do transfers yet... If there is no device on the target with known JTAG pins or it is something like a BGA with all connections hidden underneath, 1. find a pin on the connector with obvious connection to ground plane 2. find the logic voltage level (often there's at least one pin at high level when the device is powered) 3. find out which other pins are connected to something beside GND or VCC (looking at the PCB helps most) Then assuming that you already have a JTAG adapter that supports the target's voltage levels: 4. try all possible permutations of the four JTAG signals on those connected pins. With series resistors of about 100..500 ohms and low JTAG clock, you very probably won't damage anything. Actually, I've seen only very few boards where JTAG connector was different from the standard pinout of the JTAG cable for the major component on the board (usually the CPU). Only tight space sometimes makes developers use nonstandard connectors. Kolja -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
