ET3400 Address Decoder

Address decoder for use with the Heathkit ET3400 microprocessor trainer. A 74LS30 eight input NAND gate and a 74LS20 4 input NAND gate are used to decode the 16 bit address lines on the Motorola 6800 microprocessor.

The 74HCT138 three to eight line decoder uses the 16 address lines along with the R/W and VMA02 clock line to decode locations #0FFF to #7FFF.

The circuit below (2nd Photo) uses a 74HCT573 eight bit ‘D’ latch to store / output data from a specific address location.

 

 

 

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