Myth Microcontroller Documentation

Encoding of Instructions

Each instruction maps to a unique byte value which is called the operation code ('opcode') of the instruction. Operation are bit patterns that generate electric signals that drive the coordinated operations of the CPU during each instruction cycle.

This CPU uses six distinct byte 'layouts' for encoding these bit-patterns, called format groups.

Hardware Implementation

Format Groups

The five high-order bits (IB3-7) of the instruction word register feed into an encoder chip. The encoder generates 6 mutually exclusive enable signals for downstream decoders as listed in the table.