FRESTORE
FRESTORE
Restore Internal Floating-Point State
If in Supervisor State Then
FPU State Frame => Internal State
ELSE TRAP
Syntax: FRESTORE (ea)
Description:
Aborts the execution of any floating-point operation in progress and loads a
new floating-point unit internal state from the state frame located at the effective
address. The first word at the specified address is the format word of the state frame.
It specifies the size of the frame and the revision number of the floating-point unit that
created it. A format word is invalid if it does not recognize the size of the frame or the
revision number does not match the revision of the floating-point unit. If the format word
is invalid, FRESTORE aborts, and a format exception is generated. If the format word
is valid, the appropriate state frame is loaded, starting at the specified location and
proceeding through higher addresses.
The FRESTORE instruction does not normally affect the programmer’s model registers
of the floating-point coprocessor, except for the NULL state size, as described below.
It is only for restoring the user invisible portion of the machine. The FRESTORE
instruction is used with the FMOVEM instruction to perform a full context restoration of
the floating-point unit, including the floating- point data registers and system control
registers. To accomplish a complete restoration, the FMOVEM instructions are first
executed to load the programmer’s model, followed by the FRESTORE instruction to
load the internal state and continue any previously suspended operation.