Renesas RH850 Series Installation and operating instructions

Application Note
R01AN6029EJ0100 Rev.1.0 Page
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May 10, 2017
RH850 Series
CAN Transmit Procedure (CAN FD Mode)
Summary
This document describes an example of a procedure for transmitting CAN using the RH850 series. Please refer to the
notes in the latest user's manual hardware edition for the settings of each register.
Operation Confirmed Devices
This document applies to the RH850 series.
The variables described in the text are as follows.
Table 1-1 Target Devices and Variables
Variable
Target MCU
RH850/E2x
RH850/E1M-S2
RH850/P1M-E
RS-CAN FD channel number
m
0~4
0~3
0~2
GAFLIDj, GAFLMj, GAFLP0j,
GAFLP1j Register numbers
j
0~15
0~15
0~15
Transmit/Receive FIFO buffer
number
k
0~14
0~11
0~8
Receive FIFO buffer number
x
0~7
0~7
0~7
Receive buffer number
q
0~79
0~63
0~47
Transmit buffer number
p
0~79
0~63
0~47
RAM test number
r
0~63
0~63
0~63
GAFLCFGi、GTINTSTSi
register number
i
0
0
0
Number of each status register
y
0~2
0,1
0,1
The functions marked with "★" in the text are applicable to cases where 2 or more channels are installed.
In the text, CFD is omitted from the register names.
R01AN6029EJ0100
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Contents
1. Transmit Function.............................................................................................................3
2. Transmission Using Transmit Buffers...............................................................................4
3. Transmission Using Transmit/Receive FIFO Buffers ......................................................18
4. Transmission Using Transmit Queue..............................................................................26
5. Transmit History Buffer Function ....................................................................................30
6. CAN-related Interrupt Processing...................................................................................36
7. Transmit Data Padding (only in CAN FD mode) .............................................................37
8. Precautions for Processing Flow ....................................................................................38
9. Appendix........................................................................................................................39

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1. Transmit Function
The functions that can be used when transmitting CAN messages are shown below. For details on each process, refer
to the following chapters.
•・Transmit using the transmit buffer
•・Transmit using the transmit / receive FIFO buffer
•・Transmit using the transmit queue
•・Transmit history buffer function

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2. Transmission Using Transmit Buffers
The transmit buffer is used to send data frames or remote frames.
There are 16 transmit buffers per channel, which can be used as a transmit buffer, for linking to the transmit/receive
FIFO buffer (transmit mode, gateway mode★), or a transmit queue.
When using it as a transmit queue for linking to the transmit/receive FIFO buffer (transmit mode, gateway mode★),
set the corresponding TMCp register to "H'00" and the TMIEp bit of the TMIEy register to "0" (interrupt disabled). In
this case, the corresponding flags in the corresponding TMSTSp register, TMTRSTSy register, TMTARSTSy register,
TMTCSTSy register, and TMTARSTSy register do not change.
The functions of the transmit buffer are shown below. For the configuration settings for using the transmit buffer,
refer to "CAN Configuration Application Note".
•・Message transmit function
•・Transmit abort function
•・One-shot transmit function (retransmit prohibition function)
•・Transmit buffer merge mode

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2.1 Message Transmit Function
This is the function to send data frames or remote frames.
A message can be sent by setting a transmit request in the transmit buffer (the TMTR bit of the TMCp register is
“1”).
The transmission result can be confirmed by the TMTRF [1: 0] flag in the corresponding TMSTSp register. If the
transmission is successful, the transmission is completed: no transmit abort request (the TMTRF [1: 0] flag is “B'10”),
or the transmission is completed: transmit abort required (the TMTRF [1: 0] flag is “B'11”). About the transmission is
completed: transmit abort request (the TMTRF [1: 0] flag is "B'11"), refer to "2.2 Transmit abort function")
For each transmit buffer, interrupt enable/disable when transmission is completed can be set with the TMIEp bit of
the TMIECy register.
Figure 2-1 shows the operation of the transmit buffer.
Figure 2-1 Transmit Buffer Operation (Transmit from channel 0)
Transmit complete interrupt source
activated
Transmit buffer 0
Transmit buffer 1
Transmit buffer 2
Transmit buffer p
Msg1
Msg2
Msg3
Msg1
Msg2
Msg3
CAN Bus
Msg2
Msg3
Programmatically
・Transmit data set
・Transmit request set
Msg1
【Note】Transmit buffer number priority transmission
Note
Msg3
Retransmit when an arbitration
lost or an error occurs
Transmit Data

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2.1.1 Procedure for Sending Messages from Transmit Buffer
Figure 2-2 shows the procedure for sending messages from the transmit buffer.
【Note】1. For the TMTRF [1: 0] flag in the TMSTSp register, write "B'00" in channel communication mode or
channel standby mode. Do not write any value other than "B'00".
2. Rewrite the TMIDp register, TMPTRp register, and TMDFb_p register when there is no transmit request in
the corresponding transmit buffer (the TMTRM bit of the TMSTSp register is “0”).
3. Do not write to the TMIDP register, TMPTRp register, or TMDFb_p register linked to the transmit/receive
FIFO buffer.
4. When setting the standard ID in the transmit ID (the TMID [28: 0] bit of the TMIDp register), set the ID in
b10 to b0. Set b28-b11 to “0”.
5. This is valid only when the data is stored in the transmit history buffer (the THLDTE bit of the THLCCm
register is “1”, the THLE bit is “1”, and the THLEN bit of the TMIDp register is “1”).
6. Rewrite the TMCp register in channel communication mode or channel standby mode.
7. Set the TMCp register that satisfies the following conditions to "H'00".
Transmit buffer linked to transmit/receive FIFO buffer
Transmit buffer assigned to the transmit queue
8. Set the transmit request (set the TMTR bit of the TMCp register to “1”) when there is no transmit request (the
TMTRF [1: 0] flag in the TMSTSp register is “B’00”).
Figure 2-2 Procedure for Sending Messages from Transmit Buffer
2.2 Transmit Abort Function
If two or more nodes start transmitting at the same time, the node with the lower CAN ID priority will be an
START
Store messages in the transmit buffer *2.、3.
・IDE/RTR/ID*4.
・Enable/disable storage in the transmit history
buffer
・DLC
・Transmit buffer data label*5.
・送信データ
END
Set the transmit request of the corresponding
transmit buffer control register*6.、7.、8.
No
Yes
Is the transmit buffer status register
"H'00"?
Write "B'00" to the transmission buffer transmit
result flag*1.

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arbitration lost (the message will be aborted in case of one-shot transmissions, and the message will be retained
(retransmitted) in case of normal transmissions). A message will not be successfully sent unless it is sent without an
arbitration lost or while the CAN bus is idle.
In such cases, there is a transmit abort function to discard the message being retransmitted. The transmit abort
function is effective when you want to set a time limit for sending a message, or when you want to send an urgent
high-priority message.
Figure 2-3 shows an application example of the transmit abort function.
Figure 2-3 Application Example of Transmit Abort Function
Receiving
Send Message
Error
Flame
Resend Message
Receive
Transmit Request
Transmit Abort Request
(1) When you want to set a time limit for sending a message
After a specified time from the start of message transmission, you can set a time limit on message transmission by
requesting a transmit abort.
Error
Arbitration lost
Time Limit
(2) When you want to send an urgent high-priority message
If you perform a transmit abort while sending a message, the message being sent will be discarded after it detects
an arbitration lost or error, and you can send a high-priority message.
Arbitration Lost
Message①Transmit
Receive
Message②Transmit
Transmit Abort Request + Transmit Request of High-priority Message②

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When a transmit request is issued (the TMTRM bit of the TMSTSp register is “1”) and a transmit abort request is
issued to the transmit buffer (the TMTAR bit of the TMCp register is “1”), the transmit request is cancelled.
The timing of the actual abort after issuing the transmit abort request is shown below.
The message being sent or the message determined to be sent next by the priority determination of transmission
・When an arbitration lost occurs
・When an error occurs
Messages other than the above
・When a transmit abort request is issued
When the transmit abort is completed, the TMTRF [1: 0] flag in the TMSTSp register becomes “B’01” and the
transmit request is canceled (the TMTRM bit becomes “0”).
After issuing a transmit abort request to the message being sent or the message determined to be sent next by the
priority determination of transmission, if the transmission is completed successfully without an arbitration lost or error,
the transmission is completed: There is an abort request (TMTRF [1: 0] flag is “B'11”).
Figure 2-4 shows the operation during transmit abort.
Figure 2-4 Operation during Transmit Abort
Transmit buffer
Msg
Msg
CAN Bus
Msg (sending)
Transmit abort interrupt source activated
Transmit abort completed
Stop when an arbitration
lost or an error occurs
Abort request
Transmit buffer
Msg
Msg
CAN Bus
Msg
Transmission completion interrupt source activated
occurrence
Programmatically
・Transmit data set
・Transmit request set
(・One-shot request set)
Transmission completed:
There is an abort
request
Abort request
Transmit buffer 0
MsgA
MsgA
CAN Bus
MsgB
Transmit abort interrupt source activated
Transmit abort completed
before transmission
Abort request
Programmatically
・Transmit data set
・Transmit request set
(・One-shot request set)
MsgB
MsgB
Transmission
completed
Transmission data
Transmission data
Transmission data
Transmit buffer 1

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2.2.1 Transmit Abort Procedure
Figure 2-5 shows the procedure for transmit abort.
【Note】1. Rewrite the TMCp register in channel communication mode or channel standby mode.
2. Set the transmit TMCp register that satisfies the following conditions to "H'00".
Transmit buffer linked to the transmit/receive FIFO buffer
Transmit buffer assigned to the transmit queue
3. When there is a transmit request in the transmit buffer (the TMTR bit of the TMCp register is “1”), a transmit
abort request can be issued (the TMTAR bit of the TMCp register is “1”).
4. Depending on the timing, the transmission result will be transmission is completed: There is a transmit abort
(the TMTRF[1:0] flag in the TMSTSp register is "B'11"), so if the transmission result is to be determined,
please check not only if the transmission is complete (TMTRF [1:0] flag is "B'01") but also if the
transmission is completed: There is a transmit abort. Please refer to "2.4.3 Processing procedure after
transmission completion and transmit abort completion" for the procedure for confirming transmission
completion and transmit abort completion.
Figure 2-5 Transmit Abort Procedure
START
END
Set the transmit abort request of the target transmit
buffer*1.、2.、3.、4.

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2.3 One-Shot Transmission Function
When the TMOM bit of the RSCFDn(CFD)TMCp register is set to 1 (one-shot transmission is enabled), transmission is
performed only once. Even if an arbitration lost or an error occurs, retransmission is not performed.
The result of one-shot transmission can be confirmed by the TMTRF [1: 0] flag in the TMSTSp register. If the
one-shot transmission is successful, the transmit buffer transmission result status is transmission complete: no transmit
abort request (TMTRF [1: 0] flag is “B'10”) or transmission complete: There is a transmit abort request (TMTRF [1: 0]
flag will be “B'11”). If an arbitration lost or an error occurs, abort is completed (TMTRF [1: 0] flag is “B’01”). (Refer
to "2.2 Transmit Abort Function" for transmission completion: There is a transmit abort request (TMTRF [1: 0] flag is
"B'11")). Figure 2-6 shows the operation of one-shot transmission.
Figure 2-6 Operation of One-shot Transmission
Transmit buffer
Msg
Msg
CAN Bus
Msg
Transmission completion interrupt source activated
Programmatically
・Transmit data set
・Transmit request set
・One-shot request set
Transmit buffer
Msg
Msg
CAN Bus
Msg
Transmission
completed
successfully
When an arbitration lost or
an error occurs
Stop when an arbitration
lost or an error occurs
Transmission data
Transmission data
Transmission completion interrupt source activated