Rockwell Automation 1771-SPI,D17716.5.122 SPI PROTOCOL INTERFACE - Manual (Page 18)

Important Information That You Need
to Set Up the SPI Network
Chapter 2
2-4
Information to Configure the SPI Module
Configuration information that you initially transfer to the SPI module
with the MCC does several things:
identifies the devices with which it will communicate on the network
establishes the order in which it will poll the devices
sets the network’s communication rate
Then you transfer device-specific configuration to the SPI module with
one CCB for each device on the SPI network to set up the SPI module’s
memory to store specified command and status words. Each CCB defines:
the number of command words to be sent to the device via the SPI module
the number of status words to be sent to the device via the SPI module
word maps to designate the type and location of all command words
word maps to designate the type and location of all status words
Information that you Send to / Receive From Devices Via the SPI Module
Once you have successfully configured the SPI module, you transfer data to
and from the device via the SPI module with a CDB and a CDS, respectively.
The types of information that you can send to the device include:
bit commands to turn a machine on or off
setpoints such as for temperature and pressure
alarms to tell when temperature or pressure setpoints have been exceeded
The types of information that you can receive from the device include:
status bits such as to indicate if the machine is on or off
process temperatures or pressures
pressure and temperature alarm limits currently stored by the device