TestStat_H Pin

Figure 11–1 TAP Controller State Machine

Test Logic

Reset

1

0

Run-Test/Idle

0

1

Select-DR-Scan

1

Select-IR-Scan 1

0

1Capture-DR 0

1

0

Capture-IR 0

Shift-DR

0

Shift-IR

0

Values shown are for TMS.

1

 

Exit1-DR

1

 

0

 

Pause-DR

0

1

Exit1-IR 0

Pause-IR

1

1

0

Exit2-DR 1

0

0

1

Exit2-IR 1

Update-DR

1 0

Update-IR

1 0

Scan Sequence

11.4 TestStat_H Pin

Scan Sequence

MK145508.AI4

The TestStat_H pin serves two purposes. During power-up, it indicates BiST pass/fail status. After power-up, it indicates the 21264/EV67 timeout event.

The system reset forces TestStat_H to low. Tbox forces it high during the internal BiST and array initialization operations. During result extraction (DoResult state), the Tbox drives it low for 16 cycles. After that, the pin remains low if the BiST has passes, other- wise, it is asserted high and remains high until chip is reset again. Figure 11–2pictori- ally shows the behavior of the pin during the power-up operations.

Note: A system designer may sample the TestStat_H pin on the first rising edge of the SromClk_H pin to determine BiST results. After the power-up dur- ing the normal chip operation, whenever the 21264/EV67 does not retire an instruction for 2K CPU cycles, the pin is asserted high for 3 CPU cycles.

11–4Testability and Diagnostics

Alpha 21264/EV67 Hardware Reference Manual

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Compaq EV67, 21264 specifications TestStatH Pin, 11-4Testability and Diagnostics