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Effective Address Specifications
Nearly all operands for WC34000 instructions are specified using a 6-bit
effective address specification. Each effective address specification
is composed of two 3-bit sub-fields -- the mode field and the register field
-- shown below.
The value in the mode field determines which of the machines addressing
modes is to be used to locate the operand. The register field contains
the number of a register whose value is either the operand itself or is
to be used to locate the operand.