Whether the parameters of 1 and 74LS54 chips are input on or high, HC input is not allowed to be on. HC needs pull-up and pull-down resistors to determine the level when the input is invalid, but LS does not. LS pull-down strength, HC pull-up pull-down; With different working voltages, LS can only use 5V, and HC can use 2V to 6V; Different logical levels. LS is TTL level, and its low-level and high-level boundary values are 0.8V and 2.4V respectively. When the working voltage of HC is 5V, the boundary values of low level and high level are 0.3V and 3.6V, respectively.
2.74 The usage of the LS54 chip is that the 2.74LS54 chip is a 4-input NAND gate with 2-3-3-2 inputs, which can be used to realize logical functions such as logical AND, logical OR and logical NOT.