SEMic - The SEI Microcontroller Core - is a general-purpose 8-bit microcontroller core, which supports a flexible proprietary instruction set. Several versions of this core have been shipping in various configurations in customer’s products since 1993. These configurations include:

• Original Microcontroller design
• Microcontroller with onboard debugger features (breakpoints, debug space, etc)
• Enhanced stack functions (PUSH and POP instructions added), enhanced address range, etc

All versions of SEMic support the following features:

• 64K Byte Code Space
• 64K Byte Data Space
• 256 byte Scratch RAM Space
• Internal or External Code/Data Memory
• Power management features, including full Powerdown, low-power modes
• 4 - 6 Interrupt Sources
• 8-bit Arithmetic and Logic Functions, with Flags
• Shift and Rotate Instructions
• Conditional JMP Instructions
• Subroutine Calls and Returns
• 4 - 8-deep Hardware Stack for Interrupts and Subroutines
• Flexible set of MOV instructions
• Programmable Waitstates for flexible memory support
• SRAM Banking
• Two 8-bit General-Purpose IO Ports (bitwise programmable as inputs or outputs)
• Two on-board timers with prescalers
• Support for external devices (PWM, Digital/Analog logic)
• Coded in synthesizable Verilog HDL for portability
• Simulator and Assembler/Linker available for code generation

The primary application that SEMic has been used in has been in a speech and sound recognition and synthesis chip in the consumer market. The chip incorporates SEMic, as well as SEI ROM, RAM and Analog-to-Digital/ Digital-to-Analog converter cores, SEI high-power speaker-driver outputs, and customer-provided Digital Filter and PWM units. This chip integrates virtually the entire speech recognition and synthesis system, with the exeption of a few external analog components.

Similar applications could replace the Digital Filter and ADC/DAC with (for example) a flat-panel display controller such as an SEI SPC core, for a fully integrated system including display controller for low-cost hand-held applications.

Power Management Features

SEMic includes a number of power management features that make it ideal for very low-power applications. These include low-power operating modes in which the processor clock runs at a greatly reduced rate (down to divide-by-256). There are also two powerdown modes, in which the processor can completely power itself down, and be awakened either on a low-power timer count (useful for watch applications) or on an event on a general-purpose IO pin (useful for longer powerdowns).

Peripherals

SEMic has a number of peripheral core modules that accompany it - these allow a wide variety of products to be created depending on application requirements, cost trade-offs, etc. These modules include:

• ROMs
• SRAMs
• Analog-to-Digital Converters
• Digital-to-Analog Converters
• Display Controllers (SPC)

The microcontroller can also be easily integrated with customer-supplied logic to create customer-specific solutions.