Motorola MC68030 User Manual page 409

SAVE
OROER
n·l
n·2
RESTORE
OROER
31
FORMAT
23
I
15
LENGTH
I
(UNUSED, RESERVED
I
COPROCESSOR·OEPENOENT INFORMATION
·
·
·
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