Bailey Infi90 Interface to the pi system

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PI Interface to the Baily System

Process Variable
(N90 point type This is the process variable of a control station block (function code 80, 21, 22 or 23). The block address should be that of the station block.
Setpoint Read
(N90 point type This is the setpoint of a control station block. See point type 1.
Control Output Read
(N90 point type This is the control output of a control station block. See point type 1.
Ratio Index Read
(N90 point type This is the ratio index of a ratio control station block. See point type 1.
Analog Read
(N90 point type This refers to an analog output block (function code 30) in the plant loop.
Station Status
(N90 point type A station status should be defined as a digital point in the PI Server. The status is returned as a 5 byte code from the CIU. The first byte is the process variable status and the last 3 bytes are zero. The second byte contains the station mode. This station mode is converted to a digital value of 0-5 for processing by the Interface. The correlation between the mode byte and the PI digital value is:
if bit 7 is set then value = 5 (bypassed)
else if bit 6 set then value = 4 (manual lock)
else if bit 4 set then value = 3 (dig station failure)
else if bit 1 set then value = 2 (cascade/ratio)
else if bit 0 set then value = 1 (auto)
else then value = 0 (manual)
In addition, there are two more modes for the station status auto lock and cascade lock, corresponding to states 6 and 7. This addition is necessary for some sites because the lock bit and the auto bit are not mutually exclusive.

Bailey Infi90 Interface to the PI System

31
Thus, the user should set the PI digital point's digital state set to a digital state set that contains the following states:
Value
Station Mode
0
Manual
1
Auto
2
Cascade/Ratio

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