DESCRIPTION
The 89C535/89C536/89C538 are Single-Chip 8-Bit Microcontrollers manufactured in advanced CMOS process and are derivatives of the 80C51 microcontroller family. All the devices have the same instruction set as the 80C51.
The devices also have four 8-bit I/O ports, three 16-bit timer/event counters, a multi-source, two-priority-level, nested interrupt structure, UART and on-chip oscillator and timing circuits. For systems that require extra data memory capability up to 64k bytes, each can be expanded using standard TTL-compatible memories and logic.

FEATURES
• 80C51 Central Processing Unit
• 8k x 8 (89C535) 16k × 8 (89C536) or 64k × 8 (89C538), FLASH EPROM Program Memory
• 512 × 8 RAM, externally expandable to 64k × 8 Data Memory
• Three 16-bit counter/timers
• Up to 3 external interrupt request inputs
• 6 interrupt sources with 2 priority levels
• Four 8-bit I/O ports
• Full-duplex UART
• Power control modes
   – Idle mode
   – Power down mode, with wakeup from power down using external interrupt
• 44-pin PLCC and QFP packages