19.5 Note Concerning system.context

This sections explains note concerning system.context.

19.5.1 Note concerning FPU and DSP

The setting for system.context differs depending on how FPU and DSP are handled.

The recommendation setting of system.context is indicated from now on. If other than recommended setting is specified, the RI600V4 performance may be slightly deteriorated, compared to the recommended settings case.

1 ) When using MCU that incorporates FPU and DSP (accumulator)
Corresponding MCUs: RX600 series, etc.

2 ) When using MCU that does not incorporate FPU, but incorporates DSP (accumulator)
Corresponding MCUs: RX200 series, etc.

3 ) When using MCU that incorporates FPU, but does not incorporate DSP (accumulator)
Corresponding MCUs: MCUs that corresponds to this doesn't exist at the time of making of this manual.

4 ) When using MCU that incorporate neither FPU nor DSP (accumulator)
Corresponding MCUs: MCUs that corresponds to this doesn't exist at the time of making of this manual.

Note The compiler outputs floating-point arithmetic instructions only when the "-fpu" option is specified. If the "-chkfpu" option is specified in the assembler, the floating-point arithmetic instructions written in a program are detected as warning.
In no case does the compiler output the DSP function instructions. If the "-chkdsp" option is specified in the assembler, the DSP function instructions written in a program are detected as warning.

1 ) When using MCU that incorporates FPU and DSP (accumulator)

Table 19-3 When using MCU that incorporates FPU and DSP (accumulator)

Usage condition of instruction in tasks		Recommendation setting of system.context
Floating point arithmetic instructions	DSP function instructions
YES	YES	"FPSW" and "ACC" included settings essential
	NO	"FPSW" included setting essential and "ACC" excluded setting recommended
NO	YES	"ACC" included setting essential and "FPSW" excluded setting recommended
	NO	"FPSW" and "ACC" excluded settings recommended

2 ) When using MCU that does not incorporate FPU, but incorporates DSP (accumulator)

Table 19-4 When using MCU that does not incorporate FPU, but incorporates DSP (accumulator)

Usage condition of instruction in tasks		Recommendation setting of system.context
Floating point arithmetic instructions	DSP function instructions
YES	YES	Since the MCU does not incorporate FPU, floating-point arithmetic instructions cannot be used.
	NO
NO	YES	"FPSW" excluded and "ACC" included settings essential
	NO	"FPSW" excluded setting essential and "ACC" excluded settings recommended

3 ) When using MCU that incorporates FPU, but does not incorporate DSP (accumulator)

Table 19-5 When using MCU that incorporates FPU, but does not incorporate DSP (accumulator)

Usage condition of instruction in tasks		Recommendation setting of system.context
Floating point arithmetic instructions	DSP function instructions
YES	YES	Since the MCU does not incorporate DSP, DSP function instructions cannot be used.
	NO	"FPSW" included and "ACC" excluded settings essential
NO	YES	Since the MCU does not incorporate DSP, DSP function instructions cannot be used.
	NO	"ACC" excluded setting essential and "FPSW" excluded settings recommended

4 ) When using MCU that incorporate neither FPU nor DSP (accumulator)

Table 19-6 When using MCU that incorporate neither FPU nor DSP (accumulator)

Usage condition of instruction in tasks		Recommendation setting of system.context
Floating point arithmetic instructions	DSP function instructions
YES	YES	Since the MCU incorporate neither FPU nor DSP, floating-point arithmetic instructions and DSP function instructions cannot be used.
	NO
NO	YES
	NO	"FPSW" and "ACC" excluded settings essential

19.5.2 Relationship with the compiler options "-fint_register", "-base" and "-pid"

In system.context, by selecting one of choices "MIN," "MIN, ACC", "MIN, FPSW," or "MIN, ACC, FPSW," it is possible to configure the registers so that R8- R13 registers will not be saved as task context. This results in an increased processing speed.

Note, however, that such a setting of system.context is permitted in only the case where all of R8 - R13 registers are specified to be used by the compiler options "-fint_register", "-base" and "-pid".

If, in any other case, the above setting is made for system.context, the kernel will not operate normally.

- Good example:

1 ) -fint_register=4 -base=rom=R8 -base=ram=R9

2 ) -fint_register=3 -base=rom=R8 -base=ram=R9 -base=0x80000=R10

- Bad example:

3 ) No "-fint_register", "-base" and "-pid" options

4 ) -fint_register=4

5 ) -base=rom=R8 -base=ram=R9

6 ) -fint_register=3 -base=rom=R8 -base=ram=R9