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SNguy22
Beginner
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How to perform a VDR Scan Shift of a Virtual JTAG IP core to clock out information to TDO?

I want to shift out 0x00 to TDO of the JTAG port internally. I used a Virtual JTAG IP core and performed a VDR Scan Shift. However, I could not reveive 0x00 at the TDO pin of the JTAG port.

 

The TDI, TMS, TCK and TDO of Virtual JTAG IP core are connected to the TDI, TMS, TCK and TDO of my design. In my design, TDO is connected to a register assigned by 0x00.

The setting parameters of the Virtual JTAG IP core after compiling are as follows:

  • Instance Index = 0
  • IR Width = 1
  • Address = 0x10
  • USER1 DR Length = 5
  • VIR Capture Instruction = 0x0B

From outside of the device, I use an application to perform the following 3 command sequences (described in SVF format), but non of them give me 0x00 at the TDO.

  1. VDR Scan Shift with USER0 only

STATE RESET;

STATE IDLE;

SIR 10 TDI (00C);          // USER0 command

Set TDI = HIGH, go to Shift_DR state and wait for TDO go down LOW.

 

  1. VDR Scan Shift with USER1 + USER0

STATE RESET;

STATE IDLE;

SIR 10 TDI (00E);          // USER1 command

SIR 10 TDI (00C);          // USER0 command

Set TDI = HIGH, go to Shift_DR state and wait for TDO go down LOW.

 

  1. VDR Scan Shift with USER1 + ADDRESS + USER0

STATE RESET;

STATE IDLE;

SIR 10 TDI (00E);          // USER1 command

SIR 5 TDI (10);              // Shift Address = 0x10

SIR 10 TDI (00C);          // USER0 command

Set TDI = HIGH, go to Shift_DR state and wait for TDO go down LOW.

 

Please tell me the correct way to solve my problem.

 

Thank you very much!

S.T.Nguyen

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