Figure 4-9. Single Step operation requires a
SCANSetupStep()
then
SCANStep()
command.
4.2.7 Scan List Operations
The Scan List table resides on board the scanner. It contains 192 locations, allowing a scan made up of up to 192
channels. Two DLL functions provide means to write and read to this table. The table contains channel numbers
associated with the scanner channels. The SM4040 and SM4042 may contain entries with values between 1 and 40,
representing the available channel numbers. An entry of zero forces deselection of all channels. The Scan List table
may contain repetition, or a scan sequence with multiple selection of a single channel. Entries to the table are
context sensitive. The current configuration of the Scanner determines how channels numbers are treated. For
instance, an entry of 40 is not reasonable while in
FourWire
configuration. In this configuration, an entry of 1
(Channel 1) will force selection of two channels, Ch1 and Ch21.
All Auto Scan operations read the table sequentially, starting at address 0 and ending at 191. It is important to
consider the configuration of the Scanner when setting the table. The table may be written and read any time the
Scanner is not busy. Operations using the Scan List include:
SCANAutoScan(), SCANSetupStep(), SCANStep(),
SCANStepCmd()
and
SCANTrigAutoScan()
.
When several Scanners are connected to form a larger channel count, a zero entry disables al cards which are not
selected, while a valid channel values selects that channel of the active card. This way the scan can be made up of
channels from multiple Scanners. This requires that all Scanners included in the scan are loaded with the appropriate
table values. The following table shows a typical multiple card scanning operation, assuming all Scanners are in
TwoWire
configuration.
Scan Table Entries
Scanner
Number
@0 @1 @2 @3
@4 @5
@6
@7
SM4042
#0
0 0 8 0
0 0
0
1
SM4042
#1
3 40
0 18 0 0
0
0
SM4042
#2
0 0 0 0
4 5
6
0
Scanner#,
Channel
#1,Ch3 #1,Ch40
#0,Ch8 #1,Ch18 #2,Ch4 #2,5 #2,6 #0,1
Figure 4-10. Contents of the Scan List table control Auto Scan sequence.
Use the
SCANSetScanList()
function
to write to the Scanner hardware a channel value and
SCANGetScanList()
to read a value.
4.2.8 Locating Shorted Channel
The
SCANGetShortedChannel()
function scans all channels, and returns the first channel which is shorted. This
can be used to detect a channel to see if it is the appropriate one, be it at the scanner input connector or at the
optional terminal block. It is particularly useful in locating and identifying channel connection at the application end
of a wiring harness.
21
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