器件名称: 74HC191
功能描述: SN54HC191, SN74HC191 4-BIT SYNCHRONOUS UP/DOWN BINARY COUNTERS
文件大小: 157KB 共10页
简 介:SN54HC191, SN74HC191 4-BIT SYNCHRONOUS UP/DOWN BINARY COUNTERS
SCLS121B – DECEMBER 1982 – REVISED MAY 1997
D D D D D
Single Down/Up Count-Control Line Look-Ahead Circuitry Enhances Speed of Cascaded Counters Fully Synchronous in Count Modes Asynchronously Presettable With Load Control Package Options Include Plastic Small-Outline (D) and Ceramic Flat (W) Packages, Ceramic Chip Carriers (FK), and Standard Plastic (N) and Ceramic (J) 300-mil DIPs
SN54HC191 . . . J OR W PACKAGE SN74HC191 . . . D OR N PACKAGE (TOP VIEW)
B QB QA CTEN D/U QC QD GND
1 2 3 4 5 6 7 8
16 15 14 13 12 11 10 9
VCC A CLK RCO MAX/MIN LOAD C D
description
The ’HC191 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 (rippleclock) 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.
SN54HC191 . . . FK PACKAGE (TOP VIEW)
QB B NC VCC A QA CTEN NC D/U QC
4 5 6 7 8 3 2 1 20 19 18 17 16 15 14 9 10 11 12 13
CLK RCO NC MAX/M……
