TTCAN | User’s Manual | Revision 1.6 |
manual_about.fm
The transmit message objects 5…6, to be transmitted in the arbitrating time windows, may be controlled dynamically or may be restricted to specific messages. Their identifiers should have a lower priority than the Reference Message or the periodic messages.
The Trigger Memory contains two triggers for the message object 5, so the transmission of the contents of this message object could start at the beginning of the merged arbitrating time window at 0x0280 or at the second trigger at 0x0320. The second trigger cannot start a second transmission if the first transmission was successful and the application did not request a second transmission.
After the configuration, the TTCAN module synchronises itself to the TTCAN message schedule. S0 will wait for the first Reference Message to finish its initialisation. M0 and M1 may reach Initialisation Watch Trigger and raise the IWT interrupt when one of them is the first node to finish configuration and does not get a dominant acknowledge bit for its transmitted Reference Message. In this case, the application program has to restart the TTCAN module by clearing the IWT bit.
In the configuration, the transmit message objects for the arbitrating time windows are not yet activated, so there will not be any transmissions in the arbitrating time windows until the application program loads the transmit message objects and requests the transmission.
The actual time master can control the synchronisation of the TTCAN network to external events, see chapter 3.5.23.
The nodes are configured to generate an event at their Time Mark interrupt outputs TMI at Cycle Time 0x0100, 0x0200, and 0x0300. These events are intended as triggers for time measurements and for the analysis of the message schedule.
The nodes are configured to capture their Global Time at an event at their stopwatch trigger inputs SWT. The nodes’ Global Time can be monitored and compared when all SWT inputs are triggered synchronously.
The application has to serve the Application Watchdog at least once in 65 ms, else the ApW interrupt is set and the TTCAN module enters TT Error Level “Fatal Error”, stopping all communication. This error requires a
Line 1 | : CAN Control to 00C1; Line 1a: CAN Test Register to 0001 |
Line 10 | : Application Watchdog Limit to 0000 |
Line 99 | : CAN Control to 0082 |
It might be useful for software development to copy (e.g. at the start of a Basic Cycle) the content of some of the TTCAN status registers (TT Master State, TT Error Level, TUR Numerator Actual, Clock Control, Gap Control, or Stop_Watch) into periodic messages that can be monitored with the usual CAN analysing tools.
BOSCH | - 74/77 - | 11.11.02 |
