Prevent FPU register saving on interrupt

Hi Michael,

Can you please show me statements in your ISR for saving/restoring the FPU registers? 

Regards,

QJ

Hi QJ,

attached you can find the disassembly view of e.g. the UART ISR. Please note that we're compiling with the --no_stm option because of the silicon bug regarding the EMIF interface.

Kind regards,
Michael

Hi Michael,

The dis-assembly code shows that the FPU is enabled in your project, To disable the FPU, please do the following things in your CCS project:

1. comment out all the FPU related statements in sys_core.asm

2. use runtime time library which doesn't support FPU in your CCS compiler option

3. Remove the --float_support from your compiler option

Compile your project, then load the new out file to the MCU flash, then check the ISR dis-assembly. 

Regards,

QJ

Hi QJ,

actually I want to use the FPU. Maybe there's a misunderstanding here.

Let me redefine my question:
Does the compiler support any feature to get (manual) control over the FPU register saving/restoring?

Especially when dealing with very compact ISRs, the FPU context saving may already be a very big part of the overall ISRs execution time. e.g. the UART and LIN ISRs will not contain any floating point operations for sure.

Kind regards,
Michael