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Infineon Technologies TC1796 User Manual

Infineon Technologies TC1796
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TC1796
Peripheral Units (Vol. 2 of 2)
Controller Area Network (MultiCAN) Controller
User’s Manual 22-120 V2.0, 2007-07
MultiCAN, V2.0
22.5.8 Reference Message
The reference message object has a special role in the TTCAN system. It is the first entry
in the message object list for the TTCAN node (node 0 in the TC1796).
22.5.8.1 Differences to Normal CAN Messages
There are several differences between the behavior of a reference message and a
normal CAN message:
If a reference message is disturbed by an error during transmission, it is retransmitted
immediately.
If a reference message loses arbitration, it is not retransmitted, but the message on
the bus is received (arbitration of potential time masters).
For reception, no identifier bits (except the 3 least significant bits ID[2:0]) use an
acceptance mask (must be set by software). The entire identifier of the latest correct
reference message on the bus is stored in the reference message object.
For reception, the 3 least significant bits of the identifier always use the acceptance
mask 000
B
(must be set by software).
Its transmission request, indicated by the flag TTSR.REFTRG, is related only to a
reference time mark or to an external event (for synchronization). If a correct
reference message is received while REFTRG is set, REFTRG is automatically
cleared.
For transmission, the identifier bits of the reference message object are taken, except
the 3 least significant bits (ID[2:0]). They are taken from the bit field TMCR.TMPRIO.
The corresponding parts of its eight data bytes are directly connected to the TTCAN
internal values (cycle_count, master_ref_mark, etc.) according to the selected level
of the TTCAN protocol. The remaining bytes are available for free use.
The DLC of a reference message to be sent out is determined by the bit field
TTCR.RMDLC. This bit field must be at least 1 in TTCAN level 1 and at least 4 in
TTCAN level 2.
A reference message object can be selected to be a time master (a potential time
master) or a receiving device (no time master).
The reference message object must be initialized as a receive object (but the
transmission of this object leads to the reference frame). This is due to the fact that the
reception of a reference message is determined by the normal receive acceptance
filtering, whereas the transmission is a specific action, triggered by the TTCAN
extension.
Reference messages can also be transmitted by time masters that are in S2 error state
or after the Init_Watch_Trigger has been reached.

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Infineon Technologies TC1796 Specifications

General IconGeneral
BrandInfineon Technologies
ModelTC1796
CategoryController
LanguageEnglish