3.14 Compiler Support for Re-Entrant VCU Code

The --isr_save_vcu_regs compiler option generates instructions to save and restore VCU registers using the stack when interrupt service routines occur. This allows VCU code to be re-entrant. If an ISR interrupts a VCU computation, it will not impact results if this option is used.

This option can only be used if the --vcu_support option is set.

If --vcu_support is set to vcu0 or vcu2, the following instructions are added to the start/end of all ISRs:

VMOV32    *SP++,VCRC  
VMOV32    *SP++,VSTATUS

    <ISR code here>

VMOV32    VSTATUS,*--SP     
VMOV32    VCRC,*--SP

If --vcu_support is set to vcrc, the following instructions are added to the start/end of all ISRs:

VMOV32    *SP++,VCRC  
VMOV32    *SP++,VSTATUS
VMOV32    *SP++,VCRCPOLY
VMOV32    *SP++,VCRCSIZE

    <ISR code here>

VMOV32    VCRCSIZE,*--SP 
VMOV32    VCRCPOLY,*--SP
VMOV32    VSTATUS,*--SP     
VMOV32    VCRC,*--SP