Bidirectional Double Latch
Original Publication Date: 1985-Jun-01
Included in the Prior Art Database: 2005-Feb-18
A Bidirectional Double Latch (BDDL) in the first part can be used for shift register failure diagnostics in a Level Sensitive Scan Design (LSSD) environment for self-test. The BDDL design is shown in Fig. 1 which shows the regular L1-L2 double latch with the extra hardware needed to convert it to bidirectional. The extra hardware consists of three two-way AND-INVERTS, and one INVERTER (one-way AND-INVERT). The line SH is a control signal which controls the shift direction. When SH=0, a left shift is performed, and when SH=1, a right shift is performed. Q(i) is the output of the current stage; Q(i-1) and Q(i+1) are the outputs of the previous stage and next stage, respectively. The connection of BDDLs to form a bidirectional shift register is shown in Fig. 2.