MOTOROLA M68060 USER’S MANUAL D-17
FSAVE Save Internal Floating-Point State FSAVE
The following state frames apply to the MC68060.
NULL: An FSAVE instruction that generates this state frame indicates that the
floating-point unit state has not been modified since the last hardware reset
or FRESTORE instruction with a NULL state frame. This indicates that the
programmer’s model is in the reset state, with nonsignaling NANs in the
floating-point data registers and zeros in the floating-point control register,
floating-point status register, and floating-point instruction address register.
(Thus, it is not necessary to save the programmer’s model.)
IDLE: An FSAVE instruction that generates this state frame indicates that the
floating-point unit finished in an idle condition and is without any pending
exceptions waiting for the initiation of the next instruction.
EXCP: An FSAVE instruction that generates this size state frame indicates that the
floating-point unit encountered an exception while attempting to complete
the execution of the previous floating-point instructions, or that an FRE-
STORE of an EXCP frame occurred previously.
The FSAVE does not save the programmer’s model registers of the floating-point unit;
it saves only the user invisible portion of the machine. The FSAVE instruction may be
used with the FMOVEM instruction to perform a full context save of the floating-point
unit that includes the floating-point data registers and system control registers. To
accomplish a complete context save, first execute an FSAVE instruction to suspend
the current operation and save the internal state, then execute the appropriate
FMOVEM instructions to store the programmer’s model.