A CIA In 74HCT

If you owned a vintage Commodore house laptop you could now not have recognized it on the time, however it might have contained a flexible built-in circuit known as the MOS6526. This so-called CIA chip, for Complex Interface Adaptor, contained parallel and serial ports, timers, and a time-of-day counter. Like such a lot of an identical items of vintage silicon it’s lengthy out of manufacturing, so [Daniel Molina] made up our minds to copy a contemporary model of it on a PCB the usage of 74HGT CMOS common sense.

The outcome will probably be a stack of forums board that seem to be in regards to the measurement of a 3.5″ floppy disk lined in surface-mount 74 chips, and attached to the CIA socket of the Commodore by way of a ribbon cable. The base board is the one one finished to this point and comprises the knowledge course registers and parallel ports, however the succeding forums will every raise one of the chip’s different purposes.

It turns out quite extraordinary to make use of such a lot silicon to recreate a unmarried chip, however the level isn’t in fact to offer a realistic CIA alternative. Instead it’s instructive, it displays us how those interfaces paintings in addition to simply how a lot circuitry is stuffed into the chip. It’s no wonder that it’s impressed by way of the C74 Project, a TTL 6502 processor that we featured remaining yr.