Comunication description
Communication Speed Setting CAN¶
You can find it in the registry group called Common.
| Register | Description |
| C-CAN_Baudrate | Register to enter the CAN communication speed in kilobauds (20,50,100,125,250,500,800,1000). To receive the speed, the C-CAN_Settings register must be 0. The sampling point is fixed at 75% |
| C-CAN_Settings | Register for more detailed CAN bus settings. If a non-zero value is entered, the C-CAN_Baudrate register is overwritten at the calculated rate. Byte 0: TS1 Byte 1: TS2 Byte 2: SJ Byte 3: Frequency divisor, the fundamental frequency is 16MHz. |
Example of setting the speed to 500kbaud:
| Parameter | Value |
|---|---|
| SJ | 2 |
| TS1 | 2 |
| SJ | 4 |
| Frequency divisor | 11 |
| C-CAN_Settings | 0x0202040b |
Receiving and Sending Messages¶
Settings for receiving and sending messages via CAN communication. You will find them in the UserProg registry group.
CAN Status¶
| Register | Description |
| CAN_Status | bit 0: data sent, ready for the next one. bit 1 - bit 8: new data in buffers 1-8. |
Sending Messages¶
| Register | Description |
| CAN_Transmit_ID | CAN ID messages |
| CAN_Transmit_Len | message length in bytes |
| CAN_Transmit_Data_Lo | Sends the lower 32 bits of the message |
| CAN_Transmit_Data_Hi | Sends the upper 32 bits of the message |
| CAN_Transmit_Control | bit 1: sends a message bit 2: sends an RTR request (remote transmission request). Then it must be set to 0 |
To send a message, type 1 in the CAN_Transmit_Control registry. Before sending another message, it is necessary to write 0 to this register and wait for processing by the system. You can then send another message.
Receiving Messages¶
| Register | Description |
| CAN_Receive_Control | Receipt control register. |
| CAN_Recieve_Buffx_ID | Receive ID for buffer x (x = 1 - 8). |
| CAN_Receive_Buffx_Len | Number of bytes in the received message. |
| CAN_Receive_Buffx_Data_Lo | Receives the bottom 32 bits of the message |
| CAN_Receive_Buffx_Data_Hi | Receives the top 32 bits of the message |
There are 8 buffers for receiving messages.
Not all messages from CAN are received, but only those to which the buffers are set.
CAN_Recieve_Buff0_ID (or another selected buffer) is set to the required ID.
A message with the corresponding ID is loaded into this buffer.
Subsequently, writing 0x1000 to the CAN_Receive_Control registry resets the message reception and accepts the CAN_Receive_Buffx_ID changes.
After the system processes the message, the CAN_Receive_Control registry value must be set to 0.
After receiving the message, the bit for the specific buffer is set in the CAN_Status register.
To acknowledge receipt of the message, the corresponding buffer bit (same bit as in CAN_Status) is set in the CAN_Recieve Control register.
After processing by the system, the registers must be reset again.
Note
The standardized CAN protocol for TGZ is under development.