© 2000 Fairchild Semiconductor Corporation DS006420 www.fairchildsemi.com
August 1986
Revised March 2000
DM74LS279
Quad
S-R L
a
tch
DM74LS279
Quad S-R Latch
General Description
The DM74LS279 consists of four individual and indepen-
dent Set-Reset Latches with active low inputs. Two of the
four latches have an additional S input ANDed with the pri-
mary S input. A LOW on any S input while the R input is
HIGH will be stored in the latch and appear on the corre-
sponding Q output as a HIGH. A LOW on the R input while
the S input is HIGH will clear the Q output to a LOW. Simul-
taneous transition of the R and S inputs from LOW-to-
HIGH will cause the Q output to be indeterminate. Both
inputs are voltage level triggered and are not affected by
transition time of the input data.

Ordering Code:
Devices also available in Tape and Reel. Specify by appending the suffix letter “X” to the ordering code.
Connection Diagram Function Table
H = HIGH Level
L = LOW Level
Q
0
= The Level of Q before the indicated input conditions were established.
Note 1: For latches with double S inputs:
H = both S inputs HIGH
L = one or both S inputs LOW
Note 2: This output level is pseudo stable; that is, it may not persist when
the S and R inputs return to their inactive (HIGH) level.
Order Number Package Number Package Description
DM74LS279M M16A 16-Lead Small Outline Integrated Circuit (SOIC), JEDEC MS-012, 0.150 Narrow
DM74LS279N N16E 16-Lead Plastic Dual-In-Line Package (PDIP), JEDEC MS-001, 0.300 Wide
Inputs Output
S (Note 1) R Q
L L H (Note 2)
LHH
HLL
HHQ
0