4 rx mask registers, Rx mask registers -11 – Freescale Semiconductor MCF5480 User Manual
Page 581
Memory Map/Register Definition
MCF548x Reference Manual, Rev. 3
Freescale Semiconductor
21-11
The timer value is captured at the beginning of the identifier (ID) field of any frame on the CAN bus. This
captured value is written into the TIMESTAMP entry in a message buffer after a successful reception or
transmission of a message.
Writing to the timer is an indirect operation. The data is first written to an auxiliary register, then an internal
request/acknowledge procedure across clock domains is executed. All this is transparent to the user, except
for the fact that the data will take some time to be actually written to the register. If desired, software can
poll the register to discover when the data was actually written.
Reg
21.3.2.4
Rx Mask Registers
These registers are used as acceptance masks for received frame IDs. Three masks are defined: a global
mask, used for Rx buffers 0–13 and 16–63, and two more separate masks for buffers 14 and 15. The
meaning of each mask is the following:
Mask bit = 0: The corresponding incoming ID bit is “don’t care”.
Mask bit = 1: The corresponding ID bit is checked against the incoming ID bit, to see if a match
exists.
Note that these masks are used both for Standard and Extended ID formats. The value of mask registers
should not be changed while in normal operation, as locked frames that matched a message buffer (MB)
through a mask may be transferred into the MB (upon release) but may no longer match.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
TIMER
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Reg
Addr
MBAR + 0xA008 (TIMER0); 0xA808 (TIMER1)
Figure 21-6. FlexCAN Timer Register (TIMER)
Table 21-4. Mask Examples for Normal/Extended Messages
Base ID
ID28.................ID18
IDE
Extended ID
ID17......................................ID0
Match
MB2-ID
1 1 1 1 1 1 1 1 0 0 0
0
MB3-ID
1 1 1 1 1 1 1 1 0 0 0
1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
MB4-ID
0 0 0 0 0 0 1 1 1 1 1
0
MB5-ID
0 0 0 0 0 0 1 1 1 0 1
1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
MB14-ID
1 1 1 1 1 1 1 1 0 0 0
1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
Rx_Global_Mask
1 1 1 1 1 1 1 1 1 1 0
1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 1
Rx_Msg in
1
1 1 1 1 1 1 1 1 0 0 1
1
0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1
3
1