Frame Transmission - Infineon Technologies TC1728 User Manual

20.3.10.2 Frame Transmission

The process of a message object transmission is shown in
copy of the message object content to be transmitted (identifier, IDE bit, RTR = DIR bit,
DLC, including the Data Field for Data Frames) into the internal transmit buffer of the
assigned CAN node, several status flags are also served and monitored to control
consistent data handling.
The transmission process of a message object starting after the transmit acceptance
filtering is identical for Remote and Data Frames.
MSGVAL, TXRQ, TXEN0, TXEN1
A message can only be transmitted if all four bits in registers MOSTATn, MSGVAL
(Message Valid), TXRQ (Transmit Request), TXEN0 (Transmit Enable 0), TXEN1
(Transmit Enable 1) are set as shown in
equivalent with respect to the transmission process, they have different semantics:
Table 20-5 Message Transmission Bit Definitions
Bit Description
MSGVAL Message Valid
This is the main switch bit of the message object.
TXRQ Transmit Request
This is the standard transmit request bit. This bit must be set whenever a
message object should be transmitted. TXRQ is cleared by hardware at the
end of a successful transmission, except when there is new data (indicated
by NEWDAT = 1) to be transmitted.
When bit MOFCRn.STT ("Single Transmit Trial") is set, TXRQ becomes
already cleared when the contents of the message object are copied into
the transmit frame buffer of the CAN node.
A received remote request (after a Remote Frame reception) sets bit TXRQ
to request the transmission of the requested data frame.
TXEN0 Transmit Enable 0
This bit can be temporarily cleared by software to suppress the
transmission of this message object when it writes new content to the Data
Field. This avoids transmission of inconsistent frames that consist of a
mixture of old and new data.
Remote requests are still accepted when TXEN0 = 0, but transmission of
the Data Frame is suspended until transmission is re-enabled by software
(setting TXEN0).
User's Manual
MultiCAN, V2.24
Controller Area Network Controller (MultiCAN)
Figure 20-15. Although these bits are
20-45
Figure 20-19. Along with the
V1.0, 2011-12
TC1728