16.9.3 Transmission-Request Set Register (CANTRS)
When mailbox
n
is ready to be transmitted, the CPU should set the TRS[
n
] bit to 1 to start the transmission.
These bits are normally set by the CPU and cleared by the CAN module logic. The CAN module can set these
bits for a remote frame request. These bits are reset when a transmission is successful or aborted. If a mailbox
is configured as a receive mailbox, the corresponding bit in CANTRS is ignored unless the receive mailbox is
configured to handle remote frames. The TRS[
n
] bit of a receive mailbox is not ignored if the RTR bit is set.
Therefore, a receive mailbox (whose RTR is set) can send a remote frame if its TRS bit is set. Once the remote
frame is sent, the TRS[
n
] bit is cleared by the CAN module. Therefore, the same mailbox can be used to request
a data frame from another mode. If the CPU tries to set a bit while the eCAN module tries to clear it, the bit is
set.
Setting CANTRS[
n
] causes the particular message
n
to be transmitted. Several bits can be set simultaneously.
Therefore, all messages with the TRS bit set are transmitted in turn, starting with the mailbox having the highest
mailbox number (= highest priority), unless TPL bits dictate otherwise.
The bits in CANTRS are set by writing a 1 from the CPU. Writing a 0 has no effect. After power up, all bits are
cleared.
Figure 16-11. Transmission-Request Set Register (CANTRS)
31
0
TRS[31:0]
RS-0
LEGEND: RS = Read/Set; -
n
= value after reset
Table 16-10. Transmission-Request Set Register (CANTRS) Field Descriptions
Bit
Field
Value
Description
31:0
TRS[31:0]
Transmit-request-set bits
1
Setting TRS
n
commences the transmission of the message in that mailbox. Several bits can be set
simultaneously with all messages transmitted in turn.
0
No operation
Controller Area Network (CAN)
1026
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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