typedef-access in ISR

Hi,

I'm working on a project employing an XE164. In a ISR (CAN-RX-Interrupt) I want to fill a global variable with some values, then set a flag to signal the main program ok-to-read. The variable to fill is a structure, defined in the main program:

typedef struct {

unsigned char data[8];

unsigned char flags;

} t_data;

in main.c:

volatile t_data data;

The CAN-ISR is supposed to fill data[0..7] with the incoming bytes, then set flags to (e.g.) TRUE. The main program is supposed to look for the flag, handle the data, then reset the flag.

This works fine when I use a seperate variable. It does not always work, however, if "flags" is a member of a structure, like t_data.flags in the example above: It "mostly" works, but the main programm misses some new messages, about 10% of the time. Again, this does not occur if "flags" is a seperate variable.

Can anyone make sense of this? Could it be that read access by main to some other part of the structure also kills the ISR-write to the flags-part of the structure (or vv)?

Any help would be much apreciated.

Regs,
Alto Speckhardt