Programming instructions

TTL
Multisim Component Reference Guide 6-48 ni.com
6.4.82 74xx25 (Dual 4-In NOR w/Strobe)
This device contains two independent 4-input NOR gates with strobe.
NOR gate with strobe truth table:
6.4.83 74xx251 (Data Sel/MUX w/3-state Out)
This device contains full on-chip binary decoding to select one-of-eight data sources and has a
strobe-controlled three-state output.
Notes:
1. The blanking input (BI) must be open or held at a high logic level when output
functions 0 through 15 are desired. The ripple-blanking input (RBI
) must be open or
high if blanking of a decimal zero is not desired.
2. When a low logic level is applied to the blanking input (BI), all segment outputs are
low regardless of any other input.
3. When ripple-blanking input (RBI) and inputs A, B, C, and D are at a low level with
the lamp test input high, all segment outputs go low and the ripple-blanking output
(RBO) goes to a low level (response condition).
4. When the blanking input/ripple-blanking output (BI/RBO) is open or held high and a
low is applied to the lamp-test input, all segment outputs are high.
ABCDGY
1XXX10
X1XX10
XX1X10
XXX110
0000X1
XXXX01
ComponentRef.book Page 48 Thursday, December 7, 2006 10:12 AM