MC68030 Datasheet, PDF (381/602 Pages) Motorola, Inc – ENHANCED 32-BIT MICROPROCESSOR

Coprocessor Interface Description
SAVE
ORDER
RESTORE
ORDER
31
23
15
0
0
0
FORMAT
LENGTH
(UNUSED, RESERVED)
n
1
COPROCESSOR-DEPENDENT INFORMATION
n-1
2
n-2
3
1
n
Figure 10-14. Coprocessor State Frame Format in Memory
The processor stores the coprocessor format word at the lowest address of the state frame
in memory, and this word is the first word transferred for both the cpSAVE and the
cpRESTORE instructions. The word following the format word does not contain information
relevant to the coprocessor state frame, but serves to keep the information in the state frame
a multiple of four bytes in size. The number of entries following the format word (at higher
addresses) is determined.
The information in a coprocessor state frame describes a context of operation for that
coprocessor. This description of a coprocessor context includes the program invisible state
information and, optionally, the program visible state information. The program invisible
state information consists of any internal registers or status information that cannot be
accessed by the program but is necessary for the coprocessor to continue its operation at
the point of suspension. Program visible state information includes the contents of all
registers that appear in the coprocessor programming model and that can be directly
accessed using the coprocessor instruction set. The information saved by the cpSAVE
instruction must include the program invisible state information. If cpGEN instructions are
provided to save the program visible state of the coprocessor, the cpSAVE and
cpRESTORE instructions should only transfer the program invisible state information to
minimize interrupt latency during a save or restore operation.
MOTOROLA
MC68030 USER’S MANUAL
10-21