TS68882
Since the co-processor interface is based solely upon bus cycles and the TS68882 is
never a bus master, the TS68882 can be placed on either the logical or physical side of
the system memory management unit. This provides a great deal of flexibility in the sys-
tem design.
The virtual machine architecture of the TS68000 Family is supported by the co-proces-
sor interface and the TS68882 through the FSAVE and FRESTORE instructions. If the
TS68020/TS68030 detects a page fault and/or task time out, it can force the TS68882 to
stop whatever operation is in process at any time (even in the middle of the execution of
an instruction) and save the TS68882 internal state in memory.
The size of the saved internal state of the TS68882 is dependent upon what the CCU
and ECU are doing at the time that the FSAVE is executed. If the TS68882 is in the
reset state when the FSAVE instruction is received, only one word of state is transferred
to memory, which may be examined by the operating system to determine that the co-
processor programmer’s model is empty. If the co-processor is idle when the save
instruction is received, only a few words of internal state are transferred to memory. If
the TS68882 is in the middle of performing a calculation, it may be necessary to save
the entire internal state of the machine. Instructions that can complete execution in less
time than it would take to save the larger state in mid-instruction are allowed to complete
execution and then save the idle state.
Thus the size of the saved internal state is kept to a minimum. The ability to utilize sev-
eral internal state sizes greatly reduces the average context switching time.
The FRESTORE instruction permits reloading of an internal state that was saved earlier,
and continue any operation that was previously suspended. Restoring of the reset inter-
nal state functions just like a hardware reset to the TS68882 in that defaults are re-
established.
Note:
Though the TS68882 is instruction set compatible with the TS68881, the idle and busy
state frames are both 32 bytes larger on the TS68882 than on the TS68881. A unique
format word is generated by the TS68882 so that system software can detect this
difference.
Operand Data Formats
The TS68882 supports the following data formats:
•
•
•
•
•
•
•
Byte Integer (B)
Word Integer (W)
Long Word Integer (L)
Single Precision Real (S)
Double Precision Real (D)
Extended Precision Real (X)
Packed Decimal String Real (P)
The capital letters contained in parenthesis denote suffixes added to instructions in the
assembly language source to specify the data format to be used.
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2119A–HIREL–04/02
ATMEL [ ATMEL ]
