AN1105 STMicroelectronics, AN1105 Datasheet - Page 41

• Manufacturer Part Number: AN1105
• Description: ST7 PCAN PERIPHERAL DRIVER
• Manufacturer: STMicroelectronics

Figure 18. CAN_Transmit_Request Flowchart
3.2 INTERNAL FUNCTIONS AND DATA TYPES
3.2.1 Internal Data Types and Variables
3.2.1.1 Transmission FIFO
To avoid losing data, messages to be sent are queued in a 3-message length FIFO prior to
transmission.
Queue Unit
In fact, no physical CAN_Message structure is put into the queue. The objects handled are de-
scribed below:
typedef struct FIFO_Object
{ CAN_Message* message;
struct FIFO_Object* next_object;
struct FIFO_Object* preceding_object;
}FIFO_Object;
Only a pointer to the message appears in the structure, to avoid complex data manipulations.
The two following fields are pointers to other FIFO_Object structures.
message_to_send.buffer_rw=CFALSE
CAN_TRANSMIT_FAILURE
message_to_send.buffer_rw=CTRUE
CAN_TRANSMIT_FATAL
CAN_FIFO_FULL
Begin
Returns
Returns
Returns
Y
message_to_send.buffer_rw=CFALSE
message_to_send.buffer_rw=CFALSE
No message?
N
N
RUN = 0
(Result of CAN_Fill_Transmission_Buffer)
ST7 pCAN PERIPHERAL DRIVER
CAN_Fill_Transmission_Buffer
Returns status
Y
Y
CAN_In_Queue
(msg_to_send)
FIFO full?
N
41/100