The ‘138 decoder accepts three binary weighted inputs (A0, A1, A2) and when enabled, provides eight mutually exclusive, active LOW outputs (0 – 7). The device featured three Enable Inputs: two active LOW (E1, E2) and one active HIGH (E3). Every output will be HIGH unless E1 and E2 are LOW and E3 is HIGH. This multiple enable function allows easy parallel expansion of the device to a 1-of-32 (5 lines to 32 lines) decoder with just four ‘138s and one inverter.
The device 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. Enable inputs not used must be permanently tied to their appropriate active HIGH or active LOW state.
Manufactured: 1976 week 17