INTRODUCTION
The ST90158 and ST90135 microcontrollers are developed and manufactured by STMicroelectronics using a proprietary n-well CMOS process. Their performance derives from the use of a flexible 256-register programming model for ultra-fast context switching and real-time event response. The intelligent on-chip peripherals offload the ST9 core from I/O and data management processing tasks allowing critical application tasks to get the maximum use of core resources. The new-generation ST9 MCU devices now also support low power consumption and low voltage operation for power-efficient and low-cost embedded systems.

■ Register File based 8/16 bit Core Architecture with RUN, WFI, SLOW and HALT modes
■ Internal Memory:
   – EPROM/OTP/ROM 24/32/48/64K bytes
   – ROMless version available
   – RAM 768/1K/1.5K/2K bytes
■ Maximum External Memory: 64K bytes
■ 224 general purpose registers available as RAM, accumulators or index pointers (register file)
■ 67 fully programmable I/O bits
■ Fully Programmable PLL Clock Generator, with Frequency Multiplication and low frequency, low cost external crystal
■ Minimum 8-bit Instruction Cycle time: 83ns - (@ 24 MHz internal clock frequency)
■ Minimum 16-bit Instruction Cycle time: 250ns - (@ 24 MHz internal clock frequency)
■ 8 external and 1 Non-Maskable Interrupts
■ DMA Controller and Programmable Interrupt Handler
■ Single Master Serial Peripheral Interface with I2C capability
■ Two 16-bit Timers with 8-bit Prescaler, one usable as a Watchdog Timer (software and hardware)
■ Three (ST90158) or two (ST90135) 16-bit Multifunction Timers, each with an 8 bit prescaler, 12 operating modes and DMA capabilities
■ 8 channel 8-bit Analog to Digital Converter, with Automatic voltage monitoring capabilities and external reference inputs
■ Two (ST90158) or one (ST90135) Serial Communication Interfaces with asynchronous, synchronous and DMA capabilities
■ Rich Instruction Set with 14 Addressing modes
■ Division-by-Zero trap generation
■ Versatile IDE (Integrated development Environment) including Assembler, Linker, Ccompiler, Archiver, Source Level Debugger
■ Hardware tools; Real Time Emulator, EPROM Programming Board
■ Gang Programmer and Real Time Operating System available from Third parties