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Chapter
3
Remote I/O Scanner Operation
This chapter explains how a Remote I/O Scanner interacts with the modules in its remote drop, how it stores data, and how it exchanges data with a PLC or other type of system host.
Overview
The Remote I/O Scanner scans I/O modules in its remote drop in the same manner in which a Series 90±70 PLC CPU scans I/O modules in the PLC. Its internal memories store the remote drop's I/O data.
A Remote I/O Scanner communicates with the host over the Genius bus, sending up to 128 bytes of input data and receiving up to 128 bytes of output data each Genius bus scan.
HOST
BUS
CONTROLLER
|
| REMOTE DROP | a44975 | |
GENIUS |
|
|
|
|
MESSAGE | REMOTE |
|
| |
| SCAN |
| ||
INPUTS: | I/O SCANNER |
| ||
| INPUT | |||
UP TO 128 | % I | % AI |
| |
| MODULES | |||
BYTES |
|
|
| |
OUTPUTS: |
|
|
| OUTPUT |
UP TO 128 | % Q % AQ |
| ||
| MODULES | |||
BYTES |
|
|
|
PCM, GDS, and ADS modules can be located in a remote drop. There, they have direct access to the input and output data for the I/O modules in the remote drop. They also have indirect access to the host, through the Remote I/O Scanner's internal I/Otables.
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