DCAN Control Registers
1107
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Controller Area Network (DCAN) Module
23.17.24 IF3 Observation Register (DCAN IF3OBS)
The IF3 register set can automatically be updated with received message objects without the need to
Initiate the transfer from Message RAM by CPU (Additional information can be found in
The observation flags (bits [4:0]) in the IF3 Observation register are used to determine which data sections
of the IF3 Interface Register set have to be read in order to complete a DMA read cycle. After all marked
data sections are read, the DCAN is enabled to update the IF3 Interface Register set with new data.
Any access order of single bytes or half-words is supported. When using byte or half-word accesses, a
data section is marked as completed, if all bytes are read.
NOTE:
If IF3 Update Enable is used and no Observation flag is set, the corresponding message
objects will be copied to IF3 without activating the DMA request line and without waiting for
DMA read accesses.
A write access to this register aborts a pending DMA cycle by resetting the DMA line and enables
updating of IF3 Interface Register set with new data. To avoid data inconsistency, the DMA controller
should be disabled before reconfiguring IF3 observation register.
The status of the current read-cycle can be observed via status flags (Bits [12:8]).
An interrupt request may be generated by the IF3Upd flag if the DE3 bit of DCAN CTL register is set. See
the device data sheet to find out if this interrupt source is available.
With this, the observation status bits and the IF3Upd bit could be used by the application to realize the
notification about new IF3 content in polling or interrupt mode.
Figure 23-64. IF3 Observation Register (DCAN IF3OBS) [offset = 140h]
31
16
Reserved
R-0
15
14
13
12
11
10
9
8
IF3Upd
Reserved
IF3SDB
IF3SDA
IF3SC
IF3SA
IF3SM
R-0
R-0
R-0
R-0
R-0
R-0
R-0
7
5
4
3
2
1
0
Reserved
DataB
DataA
Ctrl
Arb
Mask
R-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
LEGEND: R/W = Read/Write; R = Read only; -
n
= value after reset
Table 23-25. IF3 Observation Register Field Descriptions
Bit
Field
Value
Description
31-16
Reserved
0
These bits are always read as 0. Writes have no effect.
15
IF3Upd
IF3 Update Data
0
No new data has been loaded since IF3 was last read.
1
New data has been loaded since IF3 was last read.
14-13
Reserved
0
These bits are always read as 0. Writes have no effect
12
IF3SDB
IF3 Status of Data B read access
0
All Data B bytes are already read or are not marked to be read.
1
Data B section still has data to read.
11
IF3SDA
IF3 Status of Data A read access
0
All Data A bytes are already read or are not marked to be read.
1
Data A section still has data to read.
10
IF3SC
IF3 Status of Control bits read access
0
All Control section bytes are already read or are not marked to be read.
1
Control section still has data to read.