APPENDIX C SUPPORT FOR FLOATING-POINT OPERATION COPROCESSOR

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The RI850V4 supports the floating-point operation coprocessor of the RH850.

The RI850V4 manipulates the floating-point configuration/status register (FPSR) for floating-point operation. The user can change the floating-point operation settings from processing programs as needed by changing this register value.

The value of FPSR is essentially specified independently for each processing program and is not inherited between processing programs.

However, the RI850V4 does not manipulate FPSR when an extended service call routine starts or ends. For this reason, an extended service call routine inherits the FPSR value from the previous processing executed before the extended service call routine, and the value changed in a processing program is retained after the program ends.

See table Table C-1 for the register value when each processing program is initially activated.

Table C-1 Register Values at Activation of Each Processing Program

Processing Program	Initial FPSR Value
Task	User setting
Cyclic handler	User setting
Interrupt handler	User setting
Extended service call routine	Inherits the value before activation.
Idle routine	User setting

Note 1 If a task is suspended and then resumed, the FPSR is restored to the value before the suspension.

Note 2 "User setting" for FPSR in the above table is the value specified as the FPSR register information in the system configuration file.