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Introduction
1.2. Notation Conventions
In this manual, the 36 bits of the computer word are numbered from left to right. For
example:
0 8 9 17 18 26 27 35
The following mnemonics define partial-word references:
sixth- S1 S2 S3 S4 S5 S6
word 0 5 6 11 12 17 18 23 24 29 30 35
quarter- Q1 Q2 Q3 Q4
word 0 8 9 17 18 26 27 35
third- T1 T2 T3
word 0 11 12 23 24 35
half- H1 H2
word 0 17 18 35
The 2200 Series Assembler mnemonics are used whenever machine instructions are
discussed. The Assembler mnemonics for partial-word transfers and registers are
defined in the MASM definition element MAXR$. These mnemonics are used in
assembly language programs.
The mnemonics U and XU indicate immediate data references. (The operand is taken
directly from the address portion of the instruction rather than from the main storage
referenced by that address.) The mnemonics XH1, XH2, and XU indicate that the system
will load the 18-bit value with sign extension to 36 bits (in other words, if bit 18 is a one,
bits 0 through 17 are set to one). This does not affect the store operation.
Control registers are referenced with the following mnemonics:
A0, A1,..., A15
Accumulators (A0 through A3 can also be used as index registers.)
A15+1, A15+2
Additional accumulators for double- or triple-precision instructions
1–2 7833 1733–004