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Chapter 1
Overview of the POINT I/O ASCII Modules
Module Inhibiting
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These actions take place with either a Poll command or an explicit message
that writes to the consume Assembly Object or the serial port object.
Produce Immediate and Master/Slave Handshake Option
This option defines when the ASCII module sends new data to controller.
In Produce Immediate mode (default), the ASCII module sends its most
current serial port data to the controller in response to each Poll command or
explicit message, or in response to an event.
With Master/Slave Handshake active, the ASCII module keys on the first byte
(next Transmit Record Number) of the Poll command or explicit message to
determine whether the new data from its serial port is sent to the controller.
This technique is useful when the adapter must ensure that some specific
actions have taken place before receiving the new serial data.
In this operating mode, the module sets the New Data Flag in its Serial Status
byte when a new string is received into the serial port. When the controller is
ready to receive the new data, it changes the value of the next Transmit Record
Number in the next Poll command or explicit message. Upon detection of the
next Transmit Record Number value change, the module updates its produce
buffer with the most recent serial input string.
Pad and No Pad Option
If the Pad option is selected (default), the ASCII module always sends a fixed
number of data bytes to the master. It is typically used when a Terminating
Character trigger is used to stop receiving ASCII data. This is useful if the
ASCII device that is connected to the ASCII module has varying data lengths
and the master cannot accept varying length I/O messages. The ASCII module
fills a short message with the pre-defined Pad Character. The Max Receive
Length parameter defines the data length.
If the No Pad option is selected, the ASCII module's produce I/O message
resizes itself to the length of the received ASCII data. This conserves
bandwidth, but causes scanners that do not support variable I/O sizes to
malfunction. Do not turn off Pad Mode if you do not have (or do not know if
you have) a scanner that supports variable I/O sizes. Pad Mode is ON by
default.
Module inhibiting lets you indefinitely suspend a connection, including Listen
Only connections, between an owner-controller and an I/O module without
removing the module from the configuration. This process lets you
temporarily disable a module, such as to perform maintenance.
You can use module inhibiting in the following ways:
•
You write a configuration for an I/O module but inhibit the module to
help prevent it from communicating with the owner-controller. The
Rockwell Automation Publication 1734-UM009C-EN-P - August 2022
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