Hi,
The Accepance mask registers are used to filter incoming ID. ID ranges can be used if mask register is set desirably. There is bit2bit correspondence between received ID, mask and programmed MB ID (or RXFIFO ID filter elements). The mask says if corresponding incoming ID bit is compared with programmed ID bit.
If mask bit is cleared the incoming ID bit is not compared, it is don’t care. If mask bit is set, then there must be exact match between incoming ID bit and programmed ID bit. To receive a message into a MB/RXFIFO all relevant bits with mask bit set must be equal to programmed one.
So assuming you are using individual masking scheme ( MCR[IRMQ] =1), then with setting
MB4.ID = 0x1800;
RXIMR4 = 0x1FFFFF00;
you will receive 0x1800-0x18FF IDs into MB4
BR, Petr
