User manual

Measuring Blocks cont. - Section 7-C
Label Files also allow a third label field to be defined for each of the normal measuring
block fields. This label is displayed in a balloon when the user hovers over the field. The
idea is to put "specified values" in this field:
Sample Rate: Some ECUs may not be willing to produce more than about 3.5 samples per
second when running a single group, even with the most aggressive protocol-
timing settings. Other ECUs may be much faster. Except on the slowest most ancient
PCs, this is a limitation inherent in the firmware in the ECU, not a limitation in the VCDS
software or the PC. Naturally, if two groups are being displayed simultaneously, the
sample rate drops about half what it was running a single group, and 3 groups
simultaneously runs at around 1/3. Sample Rate will vary from controller to controller.
Some controllers (particularly AG4 transmissions and Digifant-III ECU's) use a "hybrid"
data-type that requires reading a long header when changing group numbers. Viewing
multiple groups still works with these data types, but the sample rate becomes extremely
slow. If you see "Reading Header" all the time under the Sample Rate display, you'll know
you've got one of these.
In Engine controllers using KWP-2000, CAN, or UDS, there is a [Turbo] button in the top
right of the Measuring Blocks screen when using a HEX Interface. Pressing this button can
significantly speed up sampling, for example over 30 samples per second when logging a
single group in the engine controller in an early Touareg. Once you have pressed [Turbo]
you will remain in this High-Speed mode until you exit the Measuring Blocks screen:
The [Graph] button is used to open up VC-Scope, a plug-in for VCDS that allows you to
graph Measuring Group Information. See Section 32 for information on VC-Scope.
Use [Done, Go Back] to return to the Open Controller screen.