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Chapter 14
FCAN Interface Function
Preliminary User’s Manual U15839EE1V0UM00
14.2.5 Time
stamp
The FCAN system offers a time stamp capture capability at message reception and transmission. The
time stamp capture function is used to realize a synchronized, global clock in a CAN network, also
called global time system. However, the development and functionality of such a global clock system
has to be implemented by the user.
For time stamp capturing at message reception two trigger events are selectable (see Figure 9-5).
The counter value of the CAN global time system counter (CGTSC) is either captured upon the start-of-
frame signal (SOF) of the receive message or it is captured at the time the message is detected as
valid, i.e. if no error was detected until the last but one bit of the end-of-frame (EOF) was received. The
selection of the two trigger options is controlled by the TMR bit in the CxCTRL register (x = 1 to 2 for the
derivative µPD703128 (A), x = 1 to 4 for the derivatives µPD703129 (A) and µPD703129 (A1)). The
capture value itself is stored in the M_TIMEm register (m = 00 to 31) of the message buffer, for which
the received message has been accepted.
Remark:
The value of M_TIMEm register is undefined when an error occurs while receiving the mes-
sage.
Figure 14-5:
Time Stamp Capturing at Message Reception
SOF
ACK
Message
Message Buffer
EOF/message valid
CAN Global Time
System Counter
temporary buffer
capture
M_TIME
copy
SOF
ACK
Message
EOF/message valid
capture and copy
Message Buffer
M_TIME
Time stamp (reception) at SOF:
Time stamp (reception) at message EOF:
MAC
CAN Global Time
System Counter
Summary of Contents for mPD703128
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