ST20-C1 View Datasheet(PDF) - STMicroelectronics
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MFG CO.
'ST20-C1' PDF : 205 Pages View PDF
3.4 Instruction encoding
which is in turn encoded with the sequence:
pfix F; opr 9
3.4.5 Summary of encoding
The encoding mechanism has important consequences.
• 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.
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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