15
Instruction Set Reference
15 – 19
15.10
INSTRUCTION SET SYNTAX
The following sections describe instruction set syntax and other notation
conventions used in the reference page of each instruction.
15.10.1 Punctuation & Multifunction Instructions
All instructions terminate with a semicolon. A comma separates the
clauses of a multifunction instruction but does not terminate it. For
example, the statements below in Example A comprise one multifunction
instruction (which can execute in a single cycle). Example B shows two
separate instructions, requiring two instruction cycles.
Example A: One multifunction instruction
AX0 = DM(I0, M0),
a comma is used in multifunction instructions
AY0 = PM(I4, M4);
Example B: Two separate instructions
AX0 = DM(I0, M0);
a semicolon terminates an instruction
AY0 = PM(I4, M4);
15.10.2 Syntax Notation Example
Here is an example of one instruction, the ALU Add/Add with Carry
instruction:
[ IF cond ]
AR = xop +
yop ;
AF
C
yop + C
The permissible conds, xops and yops are given in a list. The conditional IF
clause is enclosed in square brackets, indicating that it is optional.
The destination register for the add operation must be either AR or AF.
These are listed within parallel bars, indicating that one of the two must
be chosen.
Similarly, the yop term may consist of a Y operand, the carry bit, or the
sum of both. One of these three terms must be used.