Testability Design-Scan Path

1, question: the principle of scanning test

Two purposes of the scanning test:

1. Realize the control of the input of the combinational logic circuit.

2, the output of the combinational logic circuit is observed.

: The current status is the output of the register, generally directly to the input port of the combined logic, through the register to scan the specific values, you can complete the control of the combination circuit input.

At the same time, the output of the current combinational logic is also connected to the input port of the register, and it is necessary to scan the current output before the test data is applied.

The entire scan test is divided into three parts:

A. Mode = 0, perform a scan operation and scan 100 (the result of the combined circuit) into the register.

B. Mode = 1, perform three scan operations, scan the test template 110 into the register, and scan the last result (100).

C.mode = 0, the circuit enters the operating mode, at this time to complete the control of the combined logic input.

Testability Design-Scan Path