RCA 70/46 - Function Call (FC)

Function Call (FC)
General Description
Format
(51)
Condition Code
Interrupt
Action
Notes
Privileged
Instructions
• This instruction is used to execute Elementary Operation (EO) routines
contained in Read Only Memory (ROM). The I field is used to specify
one
of 128 possible EO routines. The address field specifies the address of
the parameters used by the specified EO routine.
9A
o
7 8
15 16 19 20 31
• Unchanged by this instruction, however, the routine called may modify
the condition codes.
• Op Code Trap.
Power Failure.
Machine
Check.
Privileged Operation.
Addressing.
Paging Error.
Paging Queue.
Others as defined by the specifications of the routine called.
• 1. The I field specifies one of 128 possible EO routines, called Special
Functions. All 8-bit codes in which
the 24 bit is zero are available
for Special Functions. This instruction is only incorporated on the
70/46 Processor. The routine specified by the I field must be incorpo-
rated in the ROM. Otherwise, an Op Code Trap Interrupt condi-
tion occurs.
2. This instruction is available to 70/46 programs only. If it is executed
in the
70/45 mode, an Op Code Trap Interrupt condition occurs.
3.
If a location outside the available memory is addressed, an Address-
ing Interrupt condition occurs.
4. If this instruction is attempted under any of the following conditions,
a
Paging Error Interrupt condition occurs and the instruction is
terminated with unpredictable results:
a. A nonexistent Translation Table element is addressed (i.e., the
two unused bits of a segment field of a virtual address are not
zero) .
b. A 2,048-byte page is addressed in the high-order address half of
a 4,096-byte page.
c. A write operation into a location within a non-writable page is
attempted.
90