HD74HC149

Features:

·  High Speed Operation: tpd (0 - 7 to Y) = 16 ns typ (CL = 50 pF)
·  High Output Current: Fanout of 10 LSTTL Loads
·  Wide Operating Voltage: VCC = 2 to 6 V
·  Low Input Current: 1 µA max
·  Low Quiescent Supply Current: ICC (static) = 4 µA max (Ta = 25°C)


Pinout




Description

The HD74HC149 is priority encoder which has 8 input lines (0 - 7) and 8 output lies (Y0 - Y7).

HD74HC149 is the logical combination of a HD74HC148 8-3 line priority encoder driving a HD74HC138 3-8 line decoder. Only one request output can be low at a time. The output that is low is dependent on the highest priority request that is low. The order of priority is 7 highest and 0 lowest. When E input is high, all outputs are high.When a output (Y0 - Y7) is low, P output is low and this indicates active condition.