The Z86318 is a member of the Z8 MCU family of CMOS microcontrollers. This device offers on-board pull-up and pull-down resistors (ROM mask-option programmable on a nibble basis), a scalable trip-point buffer to accommodate opto-transistor outputs, and high drive ports capable of up to 20 mA current sinking per pin (3 pins maximum). The Z86318 features I/O Ports (IOL = 20 mA at VOL = 0.8V, 3 pins max.) to provide increased current sinking capabilities. These devices also offer users a selection of ROM mask options, which include a permanently enabled Watch-Dog Timer that ensures operational reliability across a broad range of application environments. For applications requiring powerful I/O capabilities, the Z86318 provides dedicated input and output lines that are grouped into three ports. These ports can be configured by means of ROM mask options (nibble-programmable) as pull ups, pull downs, or neither. There are two basic address spaces available. Program Memory, and 124 bytes of general-purpose registers.