AP29000
Connecting C166 and C500 Microcontroller to CAN
Ways of handling the SAE 81C90/91 and the CAN Module on the C167CR / C515C
Application Note 64 V 1.0, 2004-02
• Then, via the Receive Ready Registers RRR1 and RRR2, the ISR can trace for
which message object new data has been received (eg. MO 5).
{
if ((INT & 0x01) != 0)
/* if bit INT.RI is set (= a mess. has been received) */
{
if ((RRR1 & 0x20) != 0)
/* if message for object 5...*/
{
/* now the data bytes can be read */
...
When accessing one of the data bytes MSGn0 to MSGn7, automatically all ather data
bytes of this message are moved to the shadow RAM and can be accessed.
• At last, the software should clear the corresponding bit in the Receive Ready
Register (RRR1.5 here):
RRR1 = 0xDF; /* clear bit RRR1.5 */
INT.RI will be cleared by the SAE 81C90/91 if all receive interrupts have been serviced
and no more receive-ready bits are set.
6.6 How to use the Basic CAN Features of the CAN Module and the
SAE 81C90/91
6.6.1 The Basic-CAN Feature of the CAN Module
The Basic-CAN Feature of the CAN module works with message object 15 in
combination with the "Mask of Last Message" Register(s). MO 15 is a double-buffered
receive-only object. No messages can be sent with this MO (this is prevented by
hardware). It depends on the configuration of Message Configuration Register 15
which kind of frames will be stored in MO 15:
• XTD = 0, DIR = 0: Standard Data Frames
• XTD = 0, DIR = 1: Standard Remote Frames
• XTD = 1, DIR = 0: Extended Data Frames
• XTD = 1, DIR = 1: Extended Remote Frames
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