Rockwell Automation 57C421B Pulsetach Input Module/DCS 5000/AutoMax - Manual (Page 23)

4Ć1
4.0 PROGRAMMING
This section describes how the data is organized in the module and
provides examples ofhow the module can be accessed by the
application program.
4.1 Modes of Operation
The module's counter data can be utilized in one offour ways:
D positioning mode
D speed detection mode
D external latch mode
D timer mode
Each mode ofoperation is described in the following sections. Note
that the speed detection, external catch, and timer modes require
the use ofhardware interrupts for proper timing. To use the module
in these modes, the module must be located in a rack containing a
Processor module. Interrupts are not supported in remote racks.
See section 4.5 for more information about using interrupts.
4.1.1 Positioning Mode
Positioning mode is the module's default mode of operation at
power up. In this mode, the counter value is read and transferred to
the latch registers whenever the application program requests
counter data. The latch registers hold this value until the next data
request is received. The counter is not automatically reset when it is
read. See figure 4.1.
Counter
Value
Time
APPLICATION PROGRAM DATA REQUESTS
Ċ Internal Counter Value
Latched Counter Value
Figure 4.1 Ć Counter Status During Positioning Mode