Eight zeros? It is decoded by 74LS25 (double 4-input NOR gate), which is an AND gate with low effective input and high effective output. The input is all 0s and the output is 1, and the strobe terminal is connected with high level.

What are the two outputs of LS25 and? Four 1 together? CD4068(8-input NAND gate/AND gate) decodes 12 bit address, and the output terminal (J) of NAND gate is connected to the output control terminal (OE) of 74LS373; The output terminal (K) of the AND gate controls the data write terminal (LE) of 373 together with the write signal of the CPU. LE is an active high and a falling edge latch signal. Different series of CPU read and write signals are different, so you should pay attention.

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