PDP-11 Instruction Set – Opcode map

Introduction

The 65,536 values of the first word of an instruction, in octal, in ranges. A range is one instruction with its operand fields (the register or mode bits and offsets are part of the range). The Group is the feature group (models); base is on every model. A range marked reserved is no instruction in any model the decoder knows: it traps through vector 10 and is shown as .word. Every row is checked against the decoder for every word in it.

The map

Reserved words

The reserved ranges hold 1,955 of the 65,536 words:000010–000077, 000210–000227, 007100–007177, 007400–007777, 075040–076777, 107000–107777, 170003–170010 and 170013–170077. What a particular model does with them was not sourced; the decoder says only that no model it knows defines them.

Not described

Known, not yet covered

• The commercial instruction set (CIS) in 076000–076777 and the microcode-option instructions (LDUB, MED, XFC) of the models that have them.

Unknown

• What each reserved word does on each model.

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