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MC68060 Instructions
D-14
M68060 USER’S MANUAL
MOTOROLA
FRESTORE
Restore Internal
FRESTORE
Floating-Point State
(MC68060 only)
The current implementation of the MC68060 supports the following four state frames:
NULL: This state frame has a frame format of $00. An FRESTORE operation with
this state frame is equivalent to a hardware reset of the floating-point unit.
The programmer’s model is set to the reset state, with nonsignaling NANs
in the floating-point data registers and zeros in the floating-point control reg-
ister, floating-point status register, and floating-point instruction address
register. (Thus, it is unnecessary to load the programmer’s model before
this operation.)
IDLE: This state frame has a frame format of $60. An FRESTORE operation with
this state frame causes the floating-point unit to be restored to the idle state,
waiting for the initiation of the next instruction, with no exceptions pending.
The programmer’s model is not affected by loading this type of state frame.
EXCP: This state frame has a frame format of $E0. An FRESTORE operation with
this state frame causes the floating-point unit to be restored to an excep-
tional state. The exception vector field defines the type of exception that is
pending. When in this state, initiation of any floating-point instruction with
the exception of FSAVE or another FRESTORE causes the pending excep-
tion to be taken.The floating-point unit remains in this state until an FSAVE
instruction is executed, then, it enters the idle state. The programmer’s
model is not affected by loading this type of state frame.
Floating-Point Status Register:
Cleared if the state size is NULL; otherwise, not affected.
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