74LS147 10-Line to 4-Line Priority Encoder - (AD18022)

Description:

The SN54/74LS147 and SN54/74LS148 are priority encoders. They provide priority decoding of the inputs to ensure that only the highest order data line is encoded. Both devices have active-LOW data inputs and outputs.

The LS147 encodes nine data lines to four-line (8-4-2-1) BCD. The implied decimal zero condition does not require an input condition, as zero is encoded when all nine data lines are at a HIGH logic level.

The LS148 encodes eight data lines to three-line (4-2-1) binary (octal). By providing cascading circuitry (Enable Input EI and Enable Output EO), octal expansion is allowed without the need for external circuitry. The SN54/74LS748 is a proprietary Motorola device that incorporates a built-in deglitching network that minimizes glitches on the GS output. The glitch occurs on the negative transition of the EI input when data inputs 0-7 are at logic ONEs.

The only differences in DC parameters between the LS148 and LS748 are: (1) Pin 10 (input 0) has an input loading of 2 in the LS748 versus 1 in the LS148; (2) Pins 1, 2, 3, 4, 11, 12, and 13 (inputs 1, 2, 3, 4, 5, 6, 7) have an input loading of 3 in the LS748 versus 2 in the LS148. The only AC difference is that the tPHL from EI to EO is changed from 40 to 45 ns.

Datasheet