HD74HC149 Datasheet, PDF (1/9 Pages) Hitachi Semiconductor – 8-to-8-line Priority Encoder

HD74HC149
8-to-8-line Priority Encoder
Description
The HD74HC149 is priority encoder which has 8 input lines (0 - 7) and 8 output lies (Y₀ - Y₇).
It 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.
Features
• High Speed Operation: t_pd (0 - 7 to Y) = 16 ns typ (C_L = 50 pF)
• High Output Current: Fanout of 10 LSTTL Loads
• Wide Operating Voltage: V_CC = 2 to 6 V
• Low Input Current: 1 µA max
• Low Quiescent Supply Current: I_CC (static) = 4 µA max (Ta = 25°C)