Functional Description
23.3.18.3 Message RAM Representation in Debug/Suspend Mode
In debug/suspend mode, the message RAM will be memory mapped. This allows the external debug unit
to access the message RAM.
NOTE:
During debug/suspend mode, the message RAM cannot be accessed via the IFx register
sets.
Table 23-11. Message RAM Representation in Debug/Suspend Mode
31/
30/
29/
29/
27/
26/
25/
24/
23/
22/
21/
20/
19/
18/
17/
16/
Bit #
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Reserved
M 0x00
Reserved
Parity[4:0]
MXt
MDir
Rsvd
Msk[28:16]
d
M 0x04
Msk[15:0]
Rsv
Xtd
Dir
ID[28:16]
d
M 0x08
ID[15:0]
Reserved
Rsv
Msg
UMas
RmtE
Rsv
M 0x0C
Rsvd
TxIE
RxTE
EOB
Reserved
DLC[3:0]
d
Lst
k
n
d
Data 3
Data 2
M 0x10
Data 1
Data 0
Data 7
Data 6
M 0x14
Data 5
Data 4
23.3.18.4 Message RAM Representation in Direct Access Mode
When the RDA bit in the test register is set while the DCAN module is in test mode (test bit in the CAN
control register is set), the CPU has direct access to the message RAM. Due to the 32-bit bus structure,
the RAM is split into word lines to support this feature. The CPU has access to one word line at a time
only.
In RAM direct access mode, the RAM is represented by a continuous memory space within the address
frame of the DCAN module, starting at the message RAM base address.
Note: During direct access mode, the message RAM cannot be accessed via the IFx register sets.
Any read or write to the RAM addresses for RamDirectAccess during normal operation mode (TestMode
bit or RDA bit not set) will be ignored.
Table 23-12. Message RAM Representation in RAM Direct Access Mode
31/
30/
29/
29/
27/
26/
25/
24/
23/
22/
21/
20/
19/
18/
17/
16/
Bit #
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Data 4
Data 5
M 0x00
Data 6
Data 7
Data 0
Data 1
M 0x04
Data 2
Data 3
ID[27:12]
M 0x08
ID[11:0]
DLC[3:0]
Msk[28:13]
3921
SPRUH73H – October 2011 – Revised April 2013
Controller Area Network (CAN)
Copyright © 2011–2013, Texas Instruments Incorporated