JTAG daisy chain connection does not work

Hello,
I have question for mass production of rsl10sip.
I want to upload 5 devices at same time so I followed JTAG daisy chain connection which is at below.


It says that it can be used for 8 devices for programming.

When I make this , sometimes 3 devices are correctly programming , sometimes 2 devices. Why that can happen ?

I would suggest checking the signal integrity of the signals, especially the TCK line which is multi-drop. If the driver is too strong so the edges are too fast, there may be a lot of reflections on the lines causing false clock edges to be seen by some of the devices. Slowing the clock rate and lowering the clock drive strength (lowering the clock rise time) may help.

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@ceran.omur

Please check the signal integrity of the signals, especially the TCK line which is multi-drop. If the driver is too strong so the edges are too fast, there may be a lot of reflections on the lines causing false clock edges to be seen by some of the devices. Slowing the clock rate and lowering the clock drive strength (lowering the clock rise time) may help.

I tried to make slow clock rate at flash_loader program. I made it 1MHz and lower to test but nothing changes.
For TCK , do you have an example signal output ?
image
In this figure , I changed JTAG speed as I mentioned about.
How can I make lower clock rise time ?

Thank you

How can I make lower clock rise time ?

If you’re using a Segger tool I don’t believe there is a way to adjust drive strength which would affect the signal rise time.

I tried to make slow clock rate at flash_loader program. I made it 1MHz and lower to test but nothing changes.

If the clock speed isn’t the issue, it’s still possible that the signal routing is causing reflections. What is the physical wiring of the interconnect between the parts? Is this a printed circuit board or individual wires? Can you take a look at the TCK signal at each device with an oscilloscope to see if signal integrity is indeed the culprit here?