DM74LS491N ,10-Bit CounterDM54LS491/74LS49110-BitCounterJuly1989DM54LS491/74LS49110-BitCounterGeneralDescription
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DM74LS491N
10-Bit Counter
TL/L/8332
DM54LS491/74LS491
10-Bit
Counter
July 1989
DM54LS491/74LS491 10-Bit Counter
General Description
The ten-bit countercan countup, count down, set,and load LSB’s,2 MSB’sand6 middlebits highorlowasa group.
All operationsare synchronous withthe clock. SET over-
rides LOAD, COUNTand HOLD. LOAD overrides COUNT.
COUNTis conditionalon CIN, otherwiseit holds.
All outputsare enabled whenOEislow, otherwise HIGH-Z.
The24mAIOL outputsare suitablefor driving RAM/PROM
address linesin video graphics systems.
Features/Benefits CRT verticaland horizontal timing generation Bus-structured pinout 24-pin SKINNYDIP saves space TRI-STATEÉ outputs drivebus lines Low current PNP inputs reduce loading
Connection Diagram
Top View
TL/L/8332–1
Order Number DM54LS491J,
DM74LS491Jor DM74LS491N
See NSPackageNumber J24For N24C
Standard Test Load
TL/L/8332–2
Function TableCK SET LDCNTCINUP D9-D0 Q9-Q0 OperationXXXX XX X Z Hi-ZuHXX XX X H Set allHIGHuLLX XX D D LOADDuLHH XX X Q HOLDuLHL HX X Q HOLDuLHLLL X Q plus1 CountUPuLHLLH X Qminus1 CountDN
TRI-STATEÉ isaregistered trademarkof National SemiconductorCorp.
C1995National SemiconductorCorporation RRD-B30M115/PrintedinU.S.A.