Are you, or would you consider, using a 4-bit microcontroller? (original) (raw)

The one and only time I used a 4-bit machine was when I was asked to take a prototype engine controller using a Signetics 2650 and port it into a COPS400-based controller. I ended up putting the controller software into several different architectures, all of which could do the job. That COPS400 could string 16 nibbles together with BCD arithmetic operations, giving it some computational capability.

When your entire program runs on-chip and you eliminate the external bus connection, your cost starts dropping and the word length becomes far less relevent. In a high-volume situation, it is the cost of the final custom chip (IP licenses, etc.) that drive the selection. If you are only making a few ten of thousands, then you may want to look at your options. Total cost of operation, from concept to obsolescence.

4-bit sweet spot? Using BCD comes to mind, making it work for cash transactions with 7-segment displays, RFID transactions with LEDs, any small appliance with a clock/timer, locks with keypads, even personal protection such as detecting when you have been scanned at a close distance.

]]>