The 80C31 is a microprocessor ROMless devices containing three 16-bit counter/timers, a six-source, four-priority level nested interrupt structure, a serial I/O port for either multi-processor communications, I/O expansion or full duplex UART, and on-chip oscillator and clock circuits.

In particular this MHS P-80C31 had the following features :

• P80C31BH Maximum Operating Temp (øC):70
• Memory Addressing Range:64k
• Max Instruction Length (bits):24
• Number of Addressing Modes:7
• Min Instruction Length (bits):8
• Number of Maskable Interrupts:6
• Military/High-Rel:N
• Number of Interrupt Lines:2
• Package Style:DIP
• Clock Frequency - Max. (Hz):12M
• Clock Frequency - Min. (Hz):3.5M
• Description:Prog full duplex serial;111 instructions
• No. of I/O Ports:4
• # Pins:40
• Mounting Style:T
• Nom. Supp Volt:5
• Number of I/O Lines:32
• On-Chip RAM (Bytes):128
• Tech.:CMOS