migra MPB CAN
Large Format Graphics Compatible LED Display with CANopen Interface
Page 47
microSYST Systemelectronic GmbH, Am Gewerbepark 11, 92670 Windischeschenbach
+49 9681 91960-0,
+49 9681 91960-10, [email protected], www.microsyst.de
Procedure at the CANopen Side for Transmitting an RS Frame:
1. Break down the RS frame to be transmitted into sub-frames of max. 7 bytes each.
2. Transfer the sub-frames to the interface.
* Prepare the contents of the PDO to be transmitted:
* Enter frame bytes of the sub-frame to be transmitted to PDO bytes 2
through max. 8.
* PDO byte 1:
* Enter “sub-frame length” (1 to 7).
* Change the “toggle bit”.
* Set the “end bit” to 1, if no additional sub-frames need to be
transmitted.
* Transmit the PDO.
* Wait until the PDO has been transmitted.
* Wait an additional 5 ms (to allow the interface enough time to evaluate the
PDO).
* Repeat the last 4 steps until all sub-frames have been transferred.
3. Wait until the RS frame has been transmitted:
* Transmission time depends upon frame length and the utilised RS baud rate:
* = 1.3* x frame length x (10 x 1/baud rate) if no parity bit is used
* = 1.3* x frame length x (11 x 1/baud rate) if a parity bit is used
* A safety factor of 1.3 must be used because the individual frame bytes
cannot be transmitted entirely without pauses (this becomes especially
noticeable at higher baud rates between 38,400 and 115,200 baud).
*
Completion of frame transmission can also be detected by querying the “end
bit” (via SDO). The end bit is changed to 0 as soon as the transmit buffer has
been cleared, and the next frame can be transferred.