PRESETTABLE BCD/DECADE UP/DOWN COUNTERS
PRESETTABLE 4-BIT BINARY UP/DOWN COUNTERS
The SN54/74LS190 is a synchronous UP/DOWN BCD Decade (8421) Counter and the SN54/74LS191 is a synchronous UP/DOWN Modulo-16 Binary Counter. State changes of the counters are synchronous with the LOW-to-HIGH transition of the Clock Pulse input.
An asynchronous Parallel Load (PL) input overrides counting and loads the data present on the Pn inputs into the flip-flops, which makes it possible to use the circuits as programmable counters. A Count Enable (CE) input serves as the carry /borrow input in multi-stage counters. An Up/Down Count Control (U/D) input determines whether a circuit counts up or down. A Terminal Count (TC) output and a Ripple Clock (RC) output provide overflow/underflow indication and make possible a variety of methods for generating carry/borrow signals in multistage counter applications.
• Low Power . . . 90 mW Typical Dissipation
• High Speed . . . 25 MHz Typical Count Frequency
• Synchronous Counting
• Asynchronous Parallel Load
• Individual Preset Inputs
• Count Enable and Up/Down Control Inputs
• Input Clamp Diodes Limit High Speed Termination Effects