MC68030 Datasheet, PDF (400/602 Pages) Motorola, Inc – ENHANCED 32-BIT MICROPROCESSOR

Coprocessor Interface Description
10.4.5 Supervisor Check Primitive
The supervisor check primitive verifies that the main processor is operating in the supervisor
state while executing a coprocessor instruction. This primitive applies to instructions in the
general and conditional coprocessor instruction categories. Figure 10-25 shows the format
of the supervisor check primitive.
15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
1 PC 0
0
0
1
0
0
0
0
0
0
0
0
0
0
Figure 10-25. Supervisor Check Primitive Format
This primitive uses the PC bit as previously described. Bit [15] is shown as one, but during
execution of a general category instruction, this primitive performs the same operations
regardless of the value of bit [15]. If this primitive is issued with bit [15]=0 during a conditional
category instruction, however, the main processor initiates protocol violation exception
processing.
When the main processor reads the supervisor check primitive from the response CIR, it
checks the value of the S bit in the status register. If S=0 (main processor operating at user
privilege level), the main processor aborts the coprocessor instruction by writing an abort
mask (refer to 10.3.2 Control CIR) to the control CIR. The main processor then initiates
privilege violation exception processing (refer to 10.5.2.3 Privilege Violations). If the main
processor is at the supervisor privilege level when it receives this primitive, it reads the
response CIR again.
The supervisor check primitive allows privileged instructions to be defined in the
coprocessor general and conditional instruction categories. This primitive should be the first
one issued by the coprocessor during the dialog for an instruction that is implemented as
privileged.
10.4.6 Transfer Operation Word Primitive
The transfer operation word primitive requests a copy of the coprocessor instruction
operation word for the coprocessor. This primitive applies to general and conditional
category instructions. Figure 10-26 shows the format of the transfer operation word
primitive.
10-40
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