SN54LS348

8-INPUT PRIORITY ENCODERS WITH 3-STATE OUTPUTS The SN54 / 74LS348 and the SN54 / 74LS848 are eight input priority encoders which provide the 8-line to 3-line function. The outputs (A0 – A2) and inputs (0 – 7) are active low. The active low input which has the highest priority (input 7 has the highest) is represented on the outputs (output A0 is the lowest bit). An example would be if inputs 1, 2 and 4 were low, then a binary 4 would be represented on the outputs. The GS (Group Signal) output is active low when any of the inputs are low. It serves to indicate when any of the inputs are active. A0, A1 and A2 are three-state outputs. This allows for up to 64 line expansion without the need for special external circuitry. A logical one on the Enable Input (EI) forces A0, A1 ared A2 to the disabled state and outputs GS and EO to the high state. A high on all data inputs (0 – 7) together with a low on the EI input disables outputs A0, A1, and A2 and forces output GS to the high state and output EO to the low state. Use of the EI input in conjunction with the EO output provides for the capability of having priority encoding of n input signals. The LS848 has special internal circuitry providing for a greatly reduced negative going glitch on the GS (Group Signal) output and on a reduced tendency for the A0, A1 and A2 outputs to become momentarily enabled. Both of these occurrences happen when the EI input goes from a logical one to a logical zero and all data inputs (0 – 7) are held a...