TC1796
Peripheral Units (Vol. 2 of 2)
Controller Area Network (MultiCAN) Controller
User’s Manual 22-116 V2.0, 2007-07
MultiCAN, V2.0
message, the captured value becomes the reference mark REFM. The REFM value of
the previous reference mark is stored in LREFM.
The cycle time is still incremented while the reference message is received. After the end
of the correctly received reference message, the cycle time takes the value
corresponding to the length of this reference message. As a result, the cycle time seems
to start from zero each time a reference message starts (= with each new basic cycle).
Figure 22-26 Generation of the Cycle Time
The cycle control unit also delivers the values for the basic cycle and matrix cycle
handling, and provides the possibility to generate an interrupt if a new basic cycle has
started or a new matrix cycle has started. If the TTCAN node receives a reference
message, the value for BCC is taken from the reference message.
22.5.3.2 Time Marks
Each time a reference message is received correctly, the cycle control unit starts again
comparing the cycle time to the first time mark (TM 1). If one time mark is reached, it
continues with the next one. In order to be able to do an “equal-to” comparison, the time
marks have to be programmed in increasing order and the first time mark must not be
lower than the length of the reference mark.
The cycle time is used to determine the different columns of the system matrix (CSM =
column of the system matrix). These columns are defined by the time marks. These time
marks can be programmed and are valid for all columns of the system matrix.
The cycle control unit also checks the number of the current basic cycle that is indicated
by the basic cycle count BCC. The value of BCC and the value of CSM, taken together,
clearly identify each time window in the matrix cycle.
In master mode, the value BCC is transmitted as part of the reference message.
MCA05852
Equal ?
Scheduler
Cycle
Control Unit
M
U
X
TM 2
TM 1
. . . .
CSM
BCC
TM n
CYCTM
LT LTFR
REFM REFMFR
Subtract
16 7
16 (MSB)
Reference Message
Correctly Transferred
16
16 7
6
6
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