We try to test a design with an IMX6 processor using Goepel tool. This processor is in secure mode #2 this was done by the customer).
To check communication between tester and device under test, Goepel tool start communication by a "Test Byte" (8 bits).
Folow the application note AN4626, we apply the following pattern:
1) Load IR with "Security Output Challenge" opcode.
2) Apply 64+8 clocks and read on TDO "Testbyte" + "Device Unique ID" : this step is ok.
3) Load IR with "Security Enter Response" opcode.
4) Apply on TDI "TestByte" (8 bits) + "Secret Response Key" (56 bits) .Shift ( 64 clocks) : in the same time, we read the TDO output. We expect an unknow value (56 bits: Security Enter Response register init value ) and the Testbyte (8 bits).
But, in fact, we have only "0" on TDO, for the 64 clocks.
The system behaves as if the communication was down, and we cannot access other data register.
Can anyone help me?