Interfacing 64KB DRAM to AT89S52 Microcontroller

Interfacing a 64KB DRAM to AT89S52 microcontroller externally.

The firmware, upon pressing Reset, will write 0xAA into even memory addresses and 0x55 into odd memory addresses then verifies all the memory locations. If an error is found (due to removing any IC, removing the data bus, or removing any of the control signals) then the RED LED will be ON. If verification passed OK, then the GREEN LED will be ON and the memory will be read location by location, and bit 0 of each location will appear on the YELLOW LED (So this LED will flash if everything goes right). Upon RESET is pressed, the YELLOW LED will flash 5 times then the test memory write/verify cycle starts. Pressing SW1 will only verify the memory contents.

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