Measurement Computing DBK70 - Manual (Page 77)

DBK70 User’s Manual 928494 Fundamentals of Obtaining Vehicle Data 6-11
The following diagram shows how to construct the DBK70 Filter to capture the DDP response message.
The Filter provides the information for matching the header, the mode, and the DPID#. To capture 2 data
items from the same DDP response message, assign the identical Filter to 2 DBK70 channels, then set the
appropriate Index and Length in each to target just the data bytes pertaining to the desired data element.
Most networks that support DDP have a built-in timeout mechanism that turns off the continuous broadcast
of defined DDPs if the off-board diagnostic tool is no longer present. To keep the broadcast alive, the
DBK70 must periodically send a Tester Present message. Create a DBK70 channel specifically for this
purpose by assigning its Message field to C410F13F and its Update rate to 3000. This will send the
“Tester Present” message every 3 seconds from the DBK70 (address F1) to the target module (address 10).
Now that the necessary definition and request Messages and Filters have been derived, DBK70 database
records can be constructed and assigned to DBK70 output channels.
Each configured DBK70 channel has an associated Message. This Message is transmitted on the network
at a rate designated by the Update Rate field. When using DDP, multiple definition messages then one
request message must be transmitted one time by the DBK70, after which the DDP will be continually
transmitted by the associated network module.
When using DDP, all of the messages from the DBK70 to the network module that are necessary to
facilitate the DDP must be encapsulated in the Message fields of the assigned DBK70 channels.
For example, monitoring 3 parameters using 3 DBK70 channels, the following messages from the DBK70
would be required.
• Definition message to add the 1 st PID to DPID#1. Sent 1 time.
• Definition message to add the 2 nd PID to DPID#1. Sent 1 time.
• Definition message to add the 3 rd PID to DPID#1. Sent 1 time.
• Request message to initiate the transmission of DPID#1 from the network module. Sent 1 time.
• Tester Present message to tell the network module that the DBK70 is still present. Sent periodically.
These messages, sent by the DBK70, must be encapsulated in the Message fields of the 3 assigned DBK70
channels.