aci eRCM Express, Manual

Page: 95 / 97

mCore Firmware Ver 01.10 Ver 2019-Oct-29 Page 95 of 97
Allen-Bradley Handshaking
eRCM Express Software in the mCore device takes a set of inputs and calculates many outputs
that provide optimization and performance information about a compressor. The module typically
operates with a remote device that provides the inputs and consumes the outputs, and the
interaction between the data transfers from the remote device and the mCore must be carefully
managed to ensure that a coherent set of input data is used for the calculation and that a coherent
set of output data is consumed by the remote device.
This management is performed by using three handshake values:
Name Description Controlled By AB Tag Element
Request Indicates that a new calculation is requested. Remote Device ACI_PLC_REQ[0]
Busy Indicates that the calculation is in progress. mCore ACI_PLC_ACK[0]
Done Indicates that the calculation has completed. mCore ACI_PLC_ACK[1]
The diagram below shows the process:
The numbered steps are as follows:
1. The remote device sets Request to start to the process.
2. The mCore notices Request is high and sets Busy, while at the same time starting the
calculation.
3. The mCore completes the calculation and sets Done.
4. The remote device notices Done is high and clears the Request.
5. The mCore notices Request is low and clears both Done and Busy.
6. The remote device notices Done is low and can start the process again.
When mCore is acting as a master, such as in the AB Tag protocol, the mCore will read the ACI
inputs from the remote device after Step 2 but before the calculation starts and write the ACI
outputs before Step 3 but after the calculation completes.
Busy
Request
Done
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②
④
Calculation
③
⑤
⑤
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