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Scan chain operation
PO/SOD
SI
SE
CLK
PI
Scan Pattern operates in one of two modes,
1) Shift Mode.
2) Parallel Mode.
Mode(Active input) is controlled by Scan_En pin.
In Shift mode the input comes from the output of the previous scan
cells or scan input port.
In parallel mode the input to each scan element comes from the
combinational logic block.
STEPS:-
●
Initialize scan cells; SE = 1
●
Hold the scan clock off & Apply the stimulus to primary inputs; SE = 0
●
Measure PO; SE = 0.
●
Pulse the clock to capture new value in to scan cell; SE = 0.
●
Enable the scan operation to unload and measure the captured values ;
SE = 1.