Fujitsu Series 3 Manual

 
2. Configuration 
 
2. Configuration 
Figure 2-1 shows the block diagram of the CAN controller. 
Figure 2-1 CAN controller block diagram 
CAN_TX
CAN control unitCAN_RX
Message RAM
CAN Control Register
CPU interface
Message handler
ClockResetControlDataOUTDataIN
Address[7:0]
CAN controller
Interrupt
 
   CAN control unit 
Controls the CAN protocol and the serial registers fo r serial/parallel conversion to transfer send/received 
messages. 
   Message RAM 
Stores message objects 
   Registers 
All...

 
3. CAN Controller Operations 
 
3. CAN Controller Operations 
This section explains the operations and functions of the CAN controller. 
Following functions are included: 
  Message objects 
   Message transmission 
   Message reception 
   FIFO buffer function 
   Interrupt function 
   Bit timing 
   Test mode 
   Software initialization 
 
FUJITSU SEMICONDUCTOR LIMITED 
CHAPTER  21-2: CAN Controller 
MN706-00002-1v0-E 
1196 
MB9Axxx/MB9Bxxx  Series  

 
3. CAN Controller Operations 
 
3.1. Message objects 
The following explains message objects and the interface of the message RAM. 
 Message objects 
The configuration of message objects in the message RAM (excluding the MsgVal, NewDat, IntPnd, and 
TxRqst bits) is not initialized by a hardware reset. Initialize the message objects by the CPU, or set the 
MsgVal bit to disable (MsgVal = 0). Configure the CAN Bit Timing Register while the Init bit in the CAN 
Control Register is 1. 
A message object...

 
3. CAN Controller Operations 
 
Figure 3-1 Data transfer between the message interface registers and message RAM 
Start
Write to IFx Command Request Register
Busy = 1
WR/RD = 1
Read from message RAM to message interface registers
Write from message interface registers to  message RAM
Read from message RAM to message interface registers
Busy = 0
No Yes
Yes
No
 
 
FUJITSU SEMICONDUCTOR LIMITED 
CHAPTER  21-2: CAN Controller 
MN706-00002-1v0-E 
1198 
MB9Axxx/MB9Bxxx  Series  

 
3. CAN Controller Operations 
 
3.2. Message transmission 
The following explains how to configure the send message objects, and about the transmission. 
 Sending messages 
If there is no data transfer between the message interf ace registers and message RAM, the MsgVal bit in the 
CAN Message Valid Register and the TxRqst bit in  the CAN Transmit Request Register are evaluated. A 
valid message object with the highest priority of pend ing transmission requests is transferred to the shift 
register...

 
3. CAN Controller Operations 
 
 Configuring a send message object 
Ta b l e  3 - 1  shows how a send object should be initialized. 
Table 3-1 Initialization of a send message object 
MsgVal Arb Data Mask EoB Dir NewDatMsgLstRxIETxIEIntPnd RmtEn TxRqst 
1 0 1 1 0 0 0 0 appl. appl. appl. appl.appl. 
 
The IFx Arbitration Register (ID28-0 and Xtd bit), given by the application, defines the ID and the type of 
the outgoing message. 
If the standard frame (11-bit ID) is set, then ID28 to  ID18 are used,...

 
3. CAN Controller Operations 
 
 Updating a send message object   
The CPU can update the data of a send message object via the message interface registers. 
The send message object data is written by four bytes  of the corresponding IFx data register (in the unit of 
IFx data register A or IFx data register B). Therefore, the send message object cannot be changed by a 
single byte. 
To update 8-byte data, write 0x0087 to the IFx Command Mask Register, and the message number to the 
IFx Command...

 
3. CAN Controller Operations 
 
3.3. Message reception 
The following explains how to configure the receive message object and about the reception. 
 Acceptance filtering  for received messages 
When the arbitration and control field (ID + IDE + RTR + DLC) of a message is completely shifted into the 
shift register of the CAN controller, scanning of th e message RAM is started to compare matching with a 
valid message object. 
Then the arbitration field and mask data (including MsgVal, UMask, NewDat,...

 
3. CAN Controller Operations 
 
 Remote frame 
One of the following three operations  is selected when a remote frame is received. The selection depends on 
how the matching message object is configured. 
1.  Dir = 1 (Direction = Send), RmtEn = 1, UMask = 1 or 0 
Receives the matched remote frame, sets only the  TxRqst of this message object to 1, and 
automatically replies (sends) data frame to the remote frame. (Other than the TxRqst bit, the message 
object remains unchanged.)   
2.  Dir = 1...

 
3. CAN Controller Operations 
 
 Handling a received message 
The CPU can read a received message any ti me via the message interface registers. 
The following shows an example of handling a received message. Write 0x007F to the IFx Command 
Register, and a message number of the message object to the IFx Command Request Register. This 
procedure transfers a received message of the specifi ed message number from the message RAM to the 
message interface registers. Then the  NewDat bit and IntPnd bit of...