Calculator User Manual

How To Use the Instruction Descriptions
7-14
7.2.2 Operands
Operands can be constants, or assembly-time expressions referring to
memory, I/O ports, register addresses, pointers, shift counts, and a variety of
other constants. The operands category for each instruction description de-
fines the variables used for and/or within operands in the syntax expressions.
For example, for the ADD instruction, the syntax category gives these syntax
expressions:
ADD
dma [, shift ] Direct addressing
ADD
dma , 16 Direct with left shift of 16
ADD
ind [, shift [, AR n ]] Indirect addressing
ADD
ind , 16 [, AR n ] Indirect with left shift of 16
ADD #
k Short immediate addressing
ADD #
lk [, shift ] Long immediate addressing
The operands category defines the variables dma , shift , ind , n , k , and lk . For
ind , an indirect addressing variable, you supply one of the following seven
symbols:
* *+ *– *0+ *0– *BR0+ *BR0–
These symbols are defined in subsection 6.3.2,
Indirect Addressing Options ,
on page 6-9.
7.2.3 Opcode
The opcode category breaks down the various bit fields that make up each in-
struction word. When one of the fields contains a constant value derived direct-
ly from an operand, it will have the same name as that operand. The contents
of fields that do not directly relate to operands are given other names; the op-
code category either explains these names directly or refers you to a section
of this book that explains them in detail. For example, these opcodes are given
for the ADDC instruction:
ADDC
dma
1514131211109876543210
0
11000000 dma
ADDC ind [, AR n ]
1514131211109876543210
0
11000001 ARU N NAR
Note: ARU, N, and NAR are defined in Section 6.3, Indirect Addressing Mode (page 6-9).