scan register
Technology Dictionary -> scan registerSearch:
scan register
(circuit design) A digital logic circuit which can act
either as a flip-flop or as a serial shift register and
which is used to form a scan path.
The most common design is a multiplexed flip-flop:
___ ____
normal in --| | |
| |------|D Q|---- normal/scan output
scan in ----|___/ mux | |
| | |
test mode ----+ +----|> | flip-flop
| |____|
clk ---------------+
The addition of a multiplexor (mux) to each flip-flop's
input allows operation in either normal or test mode. The
output of each flip-flop goes to the normal functional logic
as well as to the scan input of the next multiplexor in the
scan path.
The other common design is level-sensitive scan design
(LSSD).
(1995-02-14)