GENERAL DESCRIPTION

The OKI MSM80C31F/MSM80C51F microcontroller is a low-power, 8-bit device implemented

in OKIs silicon-gate complementary metal-oxide semiconductor process technology.  The

device includes 4K bytes of mask programmable ROM (MSM80C51F only), 128 bytes of

data RAM, 32 I/O lines, two 16-bit timer/counters, a five-source two-level interrupt

structure, a full duplex serial port, and an oscillator and clock circuitry.  In addition, the device

has two software selectable modes for further power reduction — Idle and Power Down.  Idle

mode freezes the CPUs in-struction execution while maintaining RAM and allowing the timers,

serial port and interrupt system to continue functions.  Power Down mode saves the RAM

contents but freezes the oscillator causing all other device functions to be inoperative.