The ’HC191 devices are 4-bit synchronous, reversible, up/down binary counters. Synchronous counting operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when instructed by the steering logic. This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple-clock) counters.
The outputs of the four flip-flops are triggered on a low- to high-level transition of the clock (CLK) input if the count-enable (CTEN) input is low. A high at CTEN inhibits counting. The direction of the count is determined by the level of the down/up (D/U) input. When D/U is low, the counter counts up, and when D/U is high, it counts down.
Features
• Wide Operating Voltage Range of 2 V to 6 V
• Outputs Can Drive Up To 10 LSTTL Loads
• Low Power Consumption, 80-µA Max ICC
• Typical tpd = 13 ns
• ±4-mA Output Drive at 5 V
• Low Input Current of 1 µA Max
• Single Down/Up Count-Control Line
• Look-Ahead Circuitry Enhances Speed of Cascaded Counters
• Fully Synchronous in Count Modes
• Asynchronously Presettable With Load Control
Feature
- Wide Operating Voltage Range of 2 V to 6 V
- Outputs Can Drive Up To 10 LSTTL Loads
- Low Power Consumption, 80-μA Max ICC
- Typical tpd = 13 ns
- ±4-mA Output Drive at 5 V
- Low Input Current of 1 μA Max
- Single Down/Up Count-Control Line
- Look-Ahead Circuitry Enhances Speed of Cascaded Counters
- Fully Synchronous in Count Modes
- Asynchronously Presettable With Load Control
(Picture: Pinout)
