Features of GSM

• 80C51 Central Processing Unit
• 5 V Operating voltage from 0 to 40 MHz
• 64 kB of on-chip Flash program memory with ISP (In-System Programming) and
• IAP (In-Application Programming)
• Supports 12-clock (default) or 6-clock mode selection via software or ISP
• SPI (Serial Peripheral Interface) and enhanced UART
• PCA (Programmable Counter Array) with PWM and Capture/Compare functions
• Four 8-bit I/O ports with three high-current Port 1 pins (16 mA each)
• Three 16-bit timers/counters
• Programmable Watchdog timer (WDT)
• Eight interrupt sources with four priority levels
• Second DPTR register
• Low EMI mode (ALE inhibit)
• TTL- and CMOS-compatible logic levels.
• Brown-out detection
• Low power modes
• Power-down mode with external interrupt wake-up
• Idle mode
• PDIP40, PLCC44 and TQFP44 packages.