Following system development using M68HC711 microcontroller (MCU) devices with EPROM or one time programmable ROM (OTPROM), a final design is often implemented using an equivalent mask-programmed M68HC11 device. However, there is a quick, cost-effective alternative to this method of going to production. WSI manufactures a complete line of PSD programmable MCU peripherals that make it possible to use a ROM-less M68HC11 derivative instead of a mask-programmed device. PSD devices combine EPROM,SRAM, programmable logic for memory map decoding, programmable I/O ports, an address latch, power management, and other capabilities on a single chip. A “twin chip” solution can increase flexibility, provide expanded memory and enhanced I/O, lower power consumption, and lower cost — all with a minimum of software and hardware modifications.