18 can message data high register – Rainbow Electronics AT91CAP9S250A User Manual
Page 735
735
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
39.8.18
CAN Message Data High Register
Name:
CAN_MDHx
Access Type:
Read/Write
• MDH: Message Data High Value
When MRDY field is set in the CAN_MSRx register, the upper 32 bits of a received message are read or written by the soft-
ware application. Otherwise, the MDH value is locked by the CAN controller to send/receive a new message.
In Receive with overwrite, the CAN controller may modify MDH value while the software application reads MDH and MDL
registers. To check that MDH and MDL do not belong to different messages, the application has to check the MMI field in
the CAN_MSRx register. In this mode, the software application must re-read CAN_MDH and CAN_MDL, while the MMI bit
in the CAN_MSRx register is set.
Bytes are received/sent on the bus in the following order:
1.
CAN_MDL[7:0]
2.
CAN_MDL[15:8]
3.
CAN_MDL[23:16]
4.
CAN_MDL[31:24]
5.
CAN_MDH[7:0]
6.
CAN_MDH[15:8]
7.
CAN_MDH[23:16]
8.
CAN_MDH[31:24]
31
30
29
28
27
26
25
24
MDH
23
22
21
20
19
18
17
16
MDH
15
14
13
12
11
10
9
8
MDH
7
6
5
4
3
2
1
0
MDH