PICs, DRAMs, and Graphic Displays Build a Graphics LCD Driver

摘要

Had you seen me unsoldering 16-pin memory chips from a 1983-vintage PC motherboard, you might have wondered what rational purpose I had in mind. Let me sketch the circuitous (apt word) path that brought me to this expedient. I've always found the smaller PIC microcontrollers difficult to expand to do jobs their on-chip facilities can't handle. For example, even with an external address latch, extra RAM ties up virtually all the I/O ports. Coupling 32-KB RAM and EPROM chips to a PIC16C57 is a real pain. Interfacing to serial EEPROM is relatively simple, if slow. A serial RAM chip in the same eight-pin package would be a handy part, but if anyone makes one, I haven't heard of it. But, when the necessity arose, I found a close approximation.