ST20-C1 STMICROELECTRONICS [STMicroelectronics], ST20-C1 Datasheet - Page 28

• Manufacturer Part Number: ST20-C1
• Description: Instruction Set Reference Manual
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

3.4 Instruction encoding
which is in turn encoded with the sequence:
3.4.5
The encoding mechanism has important consequences.
To aid clarity and brevity, prefix sequences and the use of opr are not explicitly shown
in this guide. Each instruction is represented by a mnemonic, and for primary instruc-
tions an item of data, which stands for the appropriate instruction component
sequence. Hence the examples above would be just shown as: ldc 17 , add , and and .
Where appropriate, an expression may be placed in a code sequence to represent the
code needed to evaluate that expression.
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pfix F; opr 9
Summary of encoding
It produces very compact code.
It simplifies language compilation, by providing a completely uniform way of
allowing a primary instruction to take an operand of any size up to the proces-
sor word-length.
It allows these operands to be represented in a form independent of the word-
length of the processor.
It enables any number of secondary instructions to be implemented.