The Z86217/C17 are members of Zilog's Z8 family of microcontrollers designed to reduce external system components and offer easy software/hardware development tools for pointing device and trackball applications. The devices feature on-board pull-up resistors, and a scalable trip-point buffer to accommodate opto-transistor outputs. The high drive ports are capable of up to 20 mA (at VOL = 0.8-volt) current sinking per pin, with three pins maximum, providing extra sinking current capability. The Z86217/C17's permanently enabled Watch-Dog Timer (WDT) operates upon power-up of the MCU, and provides added operational reliability for pointing device and trackball environments.