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Version 2.03
2.6 System Call Instruction
This instruction provides the means by which a program
can call upon the system to perform a service.
System Call
SC-form
sc
LEV
17 /// /// // LEV // 1 /
0 6 11 16 20 27 30 31
This instruction calls the system to perform a service. A
complete description of this instruction can be found in
Book III.
The use of the LEV field is described in Book III. The
LEV values greater than 1 are reserved, and bits 0:5 of
the LEV field (instruction bits 20:25) are treated as a
reserved field.
When control is returned to the program that executed
the System Call instruction, the contents of the registers
will depend on the register conventions used by
the program providing the system service.
This instruction is context synchronizing (see Book III).
Special Registers Altered:
Dependent on the system service
Programming Note
sc serves as both a basic and an extended mnemonic.
The Assembler will recognize an sc mnemonic
with one operand as the basic form, and an
sc mnemonic with no operand as the extended
form. In the extended form the LEV operand is
omitted and assumed to be 0.
In application programs the value of the LEV operand
for sc should be 0.
Chapter 2. Branch Processor
33