DESCRIPTION
The ST72251 HCMOS Microcontroller Unit is a member of the ST7 family of Microcontrollers. The device is based on an industry-standard 8-bit core and features an enhanced instruction set. The device normally operates at a 16MHz oscillator frequency. Under software control, the ST72251 may be placed in either WAIT, SLOW or HALT modes, thus reducing power consumption. The enhanced instruction set and addressing modes afford real programming potential. In addition to standard 8-bit data management, the ST72251 features true bit manipulation, 8x8 unsigned multiplication and indirect addressing modes on the whole memory. The device includes an on-chip oscillator, CPU, program memory (ROM/OTP/EPROM versions), RAM, 22 I/O lines and the following on-chip peripherals: Analog-to-Digital converter (ADC) with 6 multiplexed analog inputs, industry standard synchronous SPI serial interface, I2C multiple Master/Slave interface, digital Watchdog, two independ ent 16-bit Timers, one featuring an External Clock Input, and both featuring Pulse Generator capabil ities, 2 Input Captures and 2 Output Compares.

■ User Program Memory (ROM/OTP/EPROM): 4 to 8K bytes
■ Data RAM: 256 bytes, including 64 bytes of stack
■ Master Reset and Power-On Reset
■ Run, Wait, Slow and Halt modes
■ 22 multifunctional bidirectional I/O lines:
   – 22 programmable interrupt inputs
   – 8 high sink outputs
   – 6 Analog alternate inputs
   – 16 Alternate Functions
   – EMI filtering
■ Programmable watchdog (WDG)
■ Two 16-bit Timers, each featuring:
   – 2 Input Captures
   – 2 Output Compares
   – External Clock input (on Timer A only)
   – PWM and Pulse Generator modes
■ Synchronous Serial Peripheral Interface (SPI)
■ Full I2C multiple Master/Slave interface
■ 8-bit Analog-to-Digital converter (6 channels)
■ 8-bit Data Manipulation
■ 63 Basic Instructions
■ 17 main Addressing Modes
■ 8 x 8 Unsigned Multiply Instruction
■ True Bit Manipulation
■ Complete Development Support on PC/DOS WINDOWS™ Real-Time Emulator
■ Full Software Package on DOS/WINDOWS™ (C-Compiler, Cross-Assembler, Debugger)