74LS190中文资料摩托罗拉数据手册PDF规格书

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

• Cascadable

• Input Clamp Diodes Limit High Speed Termination Effects