Monday, November 30, 2009

Instruction Word

There are several hundred of Microchip Microcontrollers are available based on different applications. The Microchip Microcontrollers are broken down into three groups based on the Instruction Word Bits used for programming.
  • 12-Bits Instruction Word

  • 14-Bits Instruction Word

  • 16-Bit Instruction Word

  • 24-Bit Instruction Word

All groups architecture is based on RISC architecture. Though, they share the similar architecture, the number of instruction used may vary with respect to the group. For eg., the 14-Bit has additional instructions compared to 12-Bit and so the 16-Bit, have many more additional instructions.

The selection of suitable PIC Microcontroller for the an Embedded System is the most important task. The Instruction Word Bits can be considered as one of the factor to select a microcontroller. The right selection of microcontroller on basis of Instruction Word size, can help achieve to code efficiency and reducing the required program memory.

12-Bit instruction word

Microchip's Baseline microcontroller family(8-bit) uses the 12-Bit Instruction Word. An instruction occupy one word size in memory and can execute in one instruction cycle.

Few devices, which supports 12-Bit Instruction: PIC12C508, PIC16C5X, etc....

The devices comes under 12-bit Instruction Word are not supported by PicBasic compiler. PicBasicPro provides limited support.

14-bit instruction word

Microchip's Mid-Range Microcontroller group(8-bit) uses 14-Bit Instruction Word. Mid-Range family includes many variants of PIC microcontrollers. Most of the devices can operate upto 20MHz clock rate. The instruction set consists of 35 instructions. These devices offer advanced features such as internal and external interrupt sources.

Devices, which supports 12-Bit Instruction: PIC16C554, PIC16C64, PIC16F73,PIC16F877, etc....

These devices are supported by both the PicBasic and PicBasicPro compilers.

16-bit instruction word

Microchip's High-Performance Microcontroller group(8-bit) uses 16-Bit Instruction Word. Most of the devices in this group can operate at up to 40 MHz, have 33 I/O pins, and 3 timers. They have 23 instructions in addition to the 35 instructions found on the 14-bit microcontrollers.

Devices, which supports 12-Bit Instruction: PIC16C554, PIC16C64, PIC16F73,PIC16F877, etc....

These devices are supported by both the PicBasic and PicBasicPro compilers.

These microcontrollers can be used with PicBasicPro programmer, but the PicBasic compiler, does not provide support for this family.

24-bit Instruction Word

Microchip's High-Performance dsPIC microcontroller family(16-bit) uses the 24-Bit Instruction Word. The dsPIC Microcontroller architecture is 16-bit modified Harvard Architecture with enhanced instruction set.

Devices, which supports 24-Bit Instruction: dsPIC30F DSC, dsPIC33F DSC, etc....

A wide range of development tools are available by Microchip and from Third Party support.


For detailed information and support visit the Microchip's official website www.microchip.com.

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