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LS1020A JTAG does not work

Question asked by Dainius Zilys on Jun 6, 2017
Latest reply on Jun 8, 2017 by Dainius Zilys

I'm trying to run custom PCB with LS1020A. I use J-Link as JTAG adapter.

But the LS1020A does not respond properly. Here is a log of access:

Tue Jun 06, 2017 16:07:39: Could not measure total IR len. TDO is constant high.
Tue Jun 06, 2017 16:07:39: TotalIRLen = ?, IRPrint = 0x..FFFFFFFFFFFFF814C7B00009
Tue Jun 06, 2017 16:07:39: Could not measure total IR len. TDO is constant high.
Tue Jun 06, 2017 16:07:39: TotalIRLen = ?, IRPrint = 0x..FFFFFFFFFFFFFE0C80000009
Tue Jun 06, 2017 16:07:39: Could not measure total IR len. TDO is constant high.
Tue Jun 06, 2017 16:07:39: TotalIRLen = ?, IRPrint = 0x..000000000000000000000000

There are no any other devices in the JTAG chain. No visual noise on jtag lines, pulses are nice.

RCW is hard-coded. RESET_REQ_B is released (logic 1).

Tryed with uSD card RCW + software. Situation is the same - the response on TDO is almost random, software starts running (output on UART exists). So CPU is alive, but I can't access it via JTAG to debug.

 

Tryed various JTAG clocks - 32khz - 1MHz, - no influence.

Hardware connection seems to be fine: SCAN_MODE_B, TEST_SEL_B - pull-ups to 1.8V, TRST_B connected to PORESET_B. TCK has pull-up of 10k, as recommended. System clock is 100MHz.

 

Where could be a problem?

J-Link works on LS1021A Tower board, so adapter should be compatable with my PCB as well.

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