Elmo DSP 305 manual Activate Bit Timing Parameters Switchdelay

CANopen DSP 305 Implementation Guide

MAN-CAN305IG (Ver. 1.1)

3-6

3:out of range

3.3.3Activate Bit Timing Parameters

The LSS Master's Activate Bit Timing Parameters service activates the bit timing as defined by the Configure Bit Timing Parameters service.

The switch_delay parameter specifies the length of two delay periods of equal length, which are necessary to avoid operating the bus with differing bit timing parameters. Each node performs the actual switch of the bit timing parameters switch_delay milliseconds after the reception of the command. After performing the switch, a node does not transmit any messages before the second time ´switch_delay´ has passed. This service can be performed on all LSS Slaves in ‘Configuration Mode’.

COB-ID = 7E5h
0 CS		1		2	3	4	5	6	7	8
				Switch
	21		lsb		msb		reserved by CiA for future use
				Delay

Figure 3-12 Activate Bit Timing Parameters

switch_delay:

The duration of the two periods of time to wait until the bit timing parameters switch is performed (first period). This is the length of time before any CAN message can be transmitted with the new bit timing parameters.

Note:

Nodes may have different processing times for performing the Activate Bit Timing Parameters command. Messages that are transmitted before this command may still be in the receive queue of a node. This means that a node may still transmit CAN messages with the old bit timing due to processing delay. Therefore switch_delay must be longer than the longest processing time of any node in the network. After the switch_delay time has passed, every node must perform the switch during the second switch_delay. Only after the second switch_delay has passed are all nodes guaranteed to be listening with the new bit timing parameters. Figure 3-13 shows the durations of the two switch_delays.