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SCANAbort()

command to the Scanner. Use the

SCANOpenAllChannel()

function if you wish to open the last

selected channel at the end of the scan.

Figure

4-7.

Positive edge Triggered AutoScan is a hardware initiated automatic scanning process.

4.2.5 Triggered Scan Operation

This operation requires that the Scanner be in one of the following configurations:

TwoWire

FourWire

SixWire

TwoGroups,

and

FourGroups

. The Triggered Scan operation is a hardware driven scanning process. Each step

through the Scan List table is initiated by hardware trigger event. The trigger input signal edge polarity can be
selected. The

SCANTrigScan()

function sets the Scanner into the Triggered Scan mode, in which the Scanner

expects a total of

iPoints

triggers. Once this command is issued to the Scanner, it waits for the first trigger edge to

select the first channel from the first location in the Scan List table. Following the selection of each point, the
Scanner waits for t-Actuation period, during which triggers are ignored. The Scanner responds to subsequent trigger
edges by sequentially selecting channels stored in the Scan List. The total number of points in the scan is controlled
by the

iPoints

parameter passed to the scanner by the

SCANTrigScan()

function, which must be a value between 1

and 192. This mode is concluded at the end of the number of points specified, or terminated by sending

SCANAbort()

command to the Scanner. Use the

SCANOpenAllChannel()

function if you wish to open the last

selected channel.

Figure 4-8. Positive edge Triggered Scan operation is a hardware initiated scanning process.

4.2.6 Single Step Scan Operation

This operation requires that the Scanner be in one of the following configurations:

TwoWire

FourWire

SixWire

TwoGroups,

and

FourGroups.

The Single Step Scan operation is similar to the Triggered Scan process with the

exception that each step through the Scan List table is initiated by the

SCANStep()

command rather than by

hardware trigger event. The

SCANSetupStep()

function prepares the Scanner for this operation by resetting the

Scanner’s Scan List pointer to point to the first entry of the table. In response to the

SCANStep()

command, the

Scanner selects the channel stored in the Scan List location pointed to by the Scan List pointer, then it increments
this pointer to point to the next location. The number of points in the scan is controlled by the number of times

SCANStep()

commands is issues since the last

SCANSetupStep()

function was executed. When done using the

SCANStep() and SCANSetupStep()

functions, the Scanner is going to remain with the last channel selected. The

maximum number of entries in the Scan List is 192. The polled version of

SCANStep()

SCANStepCmd()

function

maybe used if a polled control is required. Read about the usage of polled operations in the “Polled Type
Operations” section. Use the

SCANOpenAllChannel()