GENERAL DESCRIPTION
The ISSI IS80C51 and IS80C31 are high-performance microcontrollers fabricated using high-density CMOS technology. The CMOS IS80C51/31 is functionally compatible with the industry standard 80C51 microcontrollers.
The IS80C51/31 is designed with 4K x 8 ROM (IS80C51 only); 128 x 8 RAM; 32 programmable I/O lines; a serial I/O port for either multiprocessor communications, I/O expansion or full duplex UART; two 16-bit timer/counters; a six-source, two-priority-level, nested interrupt structure; and an on-chip oscillator and clock circuit. The IS80C51/31 can be expanded using standard TTL compatible memory.

FEATURES
• 80C51 based architecture
• 4K x 8 ROM (IS80C51 only)
• 128 x 8 RAM
• Two 16-bit Timer/Counters
• Full duplex serial channel
• Boolean processor
• Four 8-bit I/O ports, 32 I/O lines
• Memory addressing capability
   – 64K ROM and 64K RAM
• Power save modes:
   – Idle and power-down
• Six interrupt sources
• Most instructions execute in 0.3 µs
• CMOS and TTL compatible
• Maximum speed: 40 MHz @ Vcc = 5V
• Industrial temperature available
• Packages available:
   – 40-pin DIP
   – 44-pin PLCC
   – 44-pin PQFP