Programming instructions

74xx
 National Instruments Corporation 6-53 Multisim Component Reference Guide
6.4.91 74xx273 (Octal D-type FF)
D flip-flop truth table
6.4.92 74xx279 (Quad SR latches)
The RS flip-flop has an undesired operating condition, where 1 levels at both inputs will cause
both outputs to go to a 0 level. This undefined condition must be avoided. Circuits involving
feedback will lead to a “race condition” where the output will be unpredictable.
RS flip-flop truth table:
6.4.93 74xx28 (Quad 2-In NOR)
This device contains four independent 2-input NOR gates.
Logic function:
CLEAR CLK D Q
0 XX0
1·11
1·00
10XQ0
· = transition from low to high
SRQQ
0 0 - - (no change)
0101
1010
1 1 X X (undefined)
Y = A+B
ComponentRef.book Page 53 Thursday, December 7, 2006 10:12 AM