General

This 6393 DIN rail device can be used to monitor and control a CAN network via its RS232 interface.
The new device is ready to work on its factory defaults.

It receives CAN format messages on its RS232 input and sends these directly to the CAN bus.
With its identifier filter, it checks CAN messages on the CAN bus. Matching messages will be transmitted over the RS232 interface.

Special CAN format messages are used to control the 6393 RS232 baud rate, CAN baud rate and filter settings via the RS232 interface. These messages use 2 of the reserved CAN identifiers; 2034  and 2035.

CAN message format

A CAN message (as seen by the user) exists of 4 fields:

1. Identifier (ID, 11 bits). Allowed range 0 - 2031, reserve range 2032 - 2047
2. Remote Transmission Request (RTR, 1 bit). Used by some applications to request a message
3. Data Length (DL, 4 bits). Allowed range 0 - 15. Indicates the amount of following data bytes
4. Data. 0 - 8 bytes with application dependent data

When the RTR bit is high, the Data Length is (unmodified) ignored and no data bytes are sent with the message.

When the Data Length is greater then 8, it is treated as if it was 8.

RS232 message format

The first 3 fields of the CAN message are packed in the first 2 bytes of the RS232 message:

76543210
IIIIIIII

765
III

4
R

3210
LLLL

Although DL field can have a value from 0-15. Any value > 8 will be treated as 8.

When the RTR bit is high, no data is expected; the next received byte is interpreted as the first byte of the next CAN message....

All RS232 messages are transmitted / received with  8 data and 1 stop bit.
The Baud rate can be configured..

A ten second time-out is used when receiving RS232 messages (message is canceled when not completed within 10 seconds), this is quite long because our beloved Windows may sometimes be doing other things for a while.

To be able to synchronize a crashed application, the 6393 ignores the first byte when its value is 255 (all ones).
So sending 9 characters of all ones guaranties that the 6393 sees the first non 255 byte as a valid first byte.

To synchronize the RS232 stream to the PC, the hardware RTS output of the PC (CTS input of the 6393) can be used.
When inactive (< -5V) the 6393 does not start transmitting a new message over the RS232, although it finishes the message in progress.

When for some reason the CAN bus is so busy that the 6393 cannot send CAN messages, it de-activates its RTS output (CTS input of the PC) to stop buffer overflow / lost messages (from PC to CAN). When this happens (RTS inactive) it is still possible to send the special 6393 commands, by ignoring the handshake line.

When too many CAN messages are received (too many ID's enabled or messages are generated too fast), an internal messages lost counter is incremented. A special RS232 command is sent when this occurs. The counter can be read with a special RS232 command.

Example

We want to transmit a CAN message with CAN ID 1000, RTR = 0 and 3 data bytes (containing the ASCII characters 'CAN').

The first 2 bytes of the message have to be calculated: (ID * 32) + (RTR * 16) + DL. In our example this will be 32003, which is 7D03 hexadecimal.

5 bytes will have to be transmitted via the RS232 (all byte values are given hexadecimal).

Special commands

To be able to configure the 6393 special commands are used.
These messages are using the same format as all others, but using the reserved CAN ID's.
These messages will not be transmitted over the CAN bus.
These messages are executed even when the RTS handshake output of the 6393 is inactive.

How to get connected can be found here.

Set RS232 Baud rate

There is no reply to this message.

This command sets the RS232 speed that will be used in further RS232 communication 
(the setting is stored in EEPROM, factory default is 9600 Baud).

Set CAN Bus Speed

There is no reply to this message.

This command sets the CAN bus speed that will be used in further CAN communication 
(the setting is stored in EEPROM,  factory default is 50 kBaud).

Get CAN Bus Speed

The 6393 replies with:

Set Filter

In order to get only the CAN messages of interest, a CAN ID filter table can be set up to enable the CAN messages to receive.
This CAN ID filter table contains 1 bit for each CAN ID. The table is 256 bytes long (256 * 8 bits = 2048 ID's).

Setting up the table requires up to 64 messages to the 6393:

Some ID to byte/bit position examples;

The 6393 replies with the echo of the command (so it can be verified...)

This table will be stored in EEPROM memory, factory default is all bits set.
This storing is done in background, so the 64 setup messages can be sent without delay.

The filter setting is used in further CAN communication.

Fill Filter

In order to enable or disable all CAN ID's at once, the fill filter command fills the whole filter with the same value:

The value of the data byte is copied into all 256 locations of the ID filter

The 6393 replies with the echo of the command:

Directly after the fill filter command, the user can send one or more Set filter commands. This makes it possible to enable just one ID with only 2 messages (fill filter with all zeros, set filter with just one ID enabled at the desired index).

The table will be stored in EEPROM memory. This storing is done in background., so the fill / set messages can be sent without delay.

The filter setting is used in further CAN communication.

Get Filter

The filter settings can be read with this command:

The index value must be in the range 0 - 63.

The 6393 replies with:

Get Status

Read some internal status of the 6393:

The 6393 replies with:

Start

Start receiving CAN messages.

The 6393 replies with the echo of the command:

Only after this command is given or the start at power on configuration is set, the 6393 will relay CAN messages to its RS232 output.

Stop

Stop receiving CAN messages, clear all RS232 message buffers, some status bits and the Lost Messages counter.

The 6393 replies with the echo of the command:

RS232 speed, CAN speed, filter settings and EEPROM programming is not affected by this command. EEPROM checksum is re-checked.

Start at  power on

This command sets an internal EEPROM bit, when this bit is set, the 6293 will start relaying CAN message after power on (no start command needed). This is the factory default.

The 6393 replies with the echo of the command:

No Start at power on

This command clears an internal EEPROM bit, when this bit is clear, the 6293 will NOT start relaying CAN message after power on (no start command needed).

The 6393 replies with the echo of the command:

Reset defaults

This command executes a  stop command, then re-programs the EEPROM to some of the factory defaults.

The 6393 replies with the echo of the command:

Re-programming can take up to 0.5 second. Node has to be re-started (at 9600 Baud RS232 speed) by a power cycle or a start command.

Factory defaults.

When a 6393 node is new, or after the 'reset defaults' command, some or all of the following settings are stored in EEPROM:

How to get connected and how to use the commands

After power on the 6393 is initialized according to the  EEPROM settings for the RS232 speed, the CAN speed, the filter settings and the Start at power on bit.

How to get connected:

1. De-activate your RTS output (CTS input of 6393). This disables relaying CAN messages to the RS232 output.
   
2. Initialize the RS232 PC port with your standard application communication speed (or 9600 Baud if the 6393 is still in its factory default)
   
3. Send 9 characters FFh to the 6393 to be sure any pending message is flushed OR wait 10 seconds (when waiting 10 seconds it is guaranteed that no illegal CAN message will be send over the CAN bus)
   
4. Send the Stop command (3 bytes FEh, 61h, FEh) to the 6393 and wait for the reply (same 3 bytes).
   
5. When needed, initialize the RS232 speed, CAN speed, filter settings and Start at power on setting, activate the RTS output and send the Start command.

How to use the commands:

• Setting up the filter:
  There are several simple ways to do this when only a few ID's have to be enabled, but here a method is described that will always work.
  
  Setup the complete filter setting somewhere in your applications RAM (it's an 256 byte long byte array):
  • Fill the 256 byte array with zero's
  • For every ID to be enabled set one bit in the array:
    Index = ID shifted right 3 bits (0..2031 will be 0..253)
    Bit number = ID AND 7 (lower 3 bits)

  Send the complete filter setting by sending 64 messages to the 6393
  

• After the 6393 is started (is relaying CAN messages) it is always possible to send the special commands to it, however it is advised to send a Stop command first before changing any configuration (pending CAN messages are lost when the CAN speed is changed).
  
• Even when the CAN bus cannot send messages and the 6393's RTS output (your application's CTS input) is inactive, it is always possible to send a special 6393 command. So your RS232 transmitter should ignore the CTS input when sending a 6393 command.
  
• To synchronize / handshake the received CAN messages, the application can de-activate its RTS output (CTS input of the 6393). When RTS output is de-activated, any message in progress is finished, and a new one is started when the RTS output is started again.
  This is not true for 6393 special (reply) messages, these are send anyway (handshake is ignored).
  
• When the application is started, the 6393 will relay all CAN messages enabled by the filter. It has a 1k buffer to store messages when they are coming in faster then the RS232 can handle. This buffer can handle a burst of 100-500 CAN messages, depending on the amount of data bytes in the CAN messages.
  When this buffer overflows, the internal lost messages counter is incremented. When this happens for the first time, the 6393 sends it status (5 byte message) once over the RS232. So the application's receiver routine has to expect this.

Compatibility

The 6393 can be used by CFG6000/WIN6000 as CAN interface, the same way the 6390/6392 work (using the 6390/6392 interface mode,  see AN002).

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