The 74HC238/74HCT238 decoders accept three binary weighted address inputs (A0, A1, A2) and when enabled, provide 8 mutually exclusive active HIGH outputs (Y0 to Y7). The 74HC238/74HCT238 features three enable inputs: two active LOW (E1 and E2) and one active HIGH (E3). Every output will be LOW unless E1 and E2 are LOW and E3 is HIGH. This multiple enable function allows easy parallel expansion of the “238” to a 1-to-32 (5 lines to 32 lines) decoder with just four “238” ICs and one inverter. The “238” can be used as an eight output demultiplexer by using one of the active LOW enable inputs as the data input and the remaining enable inputs as strobes. Unused enable inputs must be permanently tied to their appropriate active HIGH or LOW state.
