Has anyone figured out the JTAG pins on a Seagate LSI chip ?

[PAKComputers]

I am trying to figure out the JTAG pins on an LSI Seagate processor.

The board I am working on is a 100535704 Rev C from a 7200.12 drive
I chose this board because it has 2 sets of header pads on the pcb --
1 is 20 pads and the other is 38 pads (also has 18 pads for the MHA)

Nothing seems to make sense on these pads
Only 3 of the pads have anything that could be a clock, but they are
pulses, not a square wave, either 30 or 60 microseconds with a 3-4uS pulse

The MPU is a LSI SEAGATE B5502D0 - 176 pin IC

[HaQue]

you need a JTAGulator!

[kostyafil]

PCB: 100535704
MPU: B5502D0

CPU ID: 0x25966041

****************
JTAG PIN MPU PIN
****************
TRST -> 16
TDI -> 18
TMS -> 20
TCK -> 17
TDO -> 19
****************

[HaQue]

nice, thanks kostyafil

[kostyafil]

But there is one problem.
The CPU does not go into "halt"

[GeorgeKJones62]

PCB: 100535704
MPU: B5502D0

CPU ID: 0x25966041

****************
JTAG PIN MPU PIN
****************
TRST -> 16
TDI -> 18
TMS -> 20
TCK -> 17
TDO -> 19
****************

Do you have any link or could you post a description of how you figured this out?

[GeorgeKJones62]

But there is one problem.
The CPU does not go into "halt"

I've seen some systems which will not halt once it's running, but will only halt when it's reset via a "reset halt". On such a system, it only works if you can find the SRST line. Which is why I'm curious how you figured out the TRST line, but not the SRST line.

[kostyafil]

Do you have any link or could you post a description of how you figured this out?

http://www.ejtag.ru/viewtopic.php?f=8&t=49

It is possible that not all the signals I found.

[skeeter]

how about the JTAG pins for either of these:

PCB: 100617465 REV B MCU: B66508

PCB: 100687658 REV C MCU: B69002V0

[fzabkar]

I have no experience with JTAG. That said, I would trace the signal pins at J6 and J104 back to their corresponding MCU pins. Hopefully there will only be a single group of 5 consecutive MCU pins. These would be your most likely JTAG candidates. Then you would only need to JTAG-ulate this group ???

[skeeter]

so i am able to jtag to the board, but cant find the SRST line to reset or halt the processor

has anyone been able to reset or halt via JTAG ?



if it were "normal" RESET should be on pin 9 of the mictor header, but it seems this is not normal.....

refs:

https://developer.arm.com/docs/dui0499/ ... 38-pinouts

https://www.segger.com/products/debug-p ... 8-adapter/