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| PV (Process Variable)<<BR>> EPICS record<<BR>> EPICS channel |
PV (Process Variable)<<BR>> EPICS record<<BR>> EPICS channel |
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| These PVs read or write into hardware channels, for example: channel 1 of Y-End ADC, channel 6 of X-End DI and so on. These PVs have names such as K1:PLC-YEND_ADC_Ch1 or K1:PLC-XEND_DI_Ch6. The names do not contain the information of what is connected. So users of the PLC system should create User PVs to have more meaningful names. The PLC administrator (currently Aso) will make all the hardware channels available as hardware PVs. |
These PVs read or write into hardware channels, for example: channel 1 of Y-End ADC, channel 6 of X-End DI and so on. These PVs have names such as K1:PLC-YEND_ADC_Ch1 or K1:PLC-XEND_DI_Ch6. The names do not contain the information of what is connected. So users of the PLC system should create User PVs to have more meaningful names. The PLC administrator (currently Aso) will make all the hardware channels available as hardware PVs. |
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EPICS interface for the PLC system
Contents
Overview
PLC system holds signal values in its internal registers. By reading the register values or writing values into the registers, we can communicate with the PLC system.
EPICS translator is a software translating the PLC register values to EPICS process variables (PVs). It can also transfer EPICS PV values into PLC registers.
The EPICS translator is implemented as an EPICS IOC. It is running on a computer called k1kiki0 (the name should be changed to k1plc0). Physical location of this computer is the PLC rack in the center area. You can login to this computer from the KAGRA control network with the controls account.
A note on EPICS terminology
The following words are used to mean basically the same thing.
PV (Process Variable)
EPICS record
EPICS channel
"PV" and "record" are correct EPICS terms. "Channel" is widely used to mean PV or record, but it is a misuse.
How to add/modify PLC related EPICS PVs
As a policy, the PLC system provide two classes of EPICS PVs.
- Hardware PVs
These PVs read or write into hardware channels, for example: channel 1 of Y-End ADC, channel 6 of X-End DI and so on. These PVs have names such as K1:PLC-YEND_ADC_Ch1 or K1:PLC-XEND_DI_Ch6. The names do not contain the information of what is connected. So users of the PLC system should create User PVs to have more meaningful names. The PLC administrator (currently Aso) will make all the hardware channels available as hardware PVs.
- User PVs
These PVs read one or more hardware PVs and (optionally) do some calculations to produce physically meaningful values and PV names. For example, assuming that a vacuum gauge is connected to Y-End ADC Ch1 and the corresponding hardware PV is K1:PLC-YEND_ADC_Ch1, you can create an user PV with the following database definition.
abc
Adding a hardware PVs (usually not necessary for users)
https://www.dropbox.com/sh/hoxx8cef5m693r7/AABv2Zk5iwK2HK9kssP4kaECa?dl=0