Woodward 505XT, Installation And Operation Manual, Page: 202 / 242

Manual 35018V1 505XT Digital Control System for Steam Turbines
Woodward 200
Analog Reads (Input Registers)
Input registers are analog values that are readable from, but not writable to, the 505 control. An example
of an analog read value would be turbine speed. The values of the input registers are stored internal to
the control as floating point numbers representing engineering units (kPa or rpm). The values that are
transmitted are integer values ranging from -32767 to +32767. Since Modbus can only handle integers,
values that have a decimal point are multiplied by a constant before being sent by Modbus. For example,
these input registers may be listed as the Modbus value `x100’ or `x10’ under the description heading to
denote the value is multiplied by a scaling constant. This will allow transmission of decimal parts of a unit
if this is necessary for better resolution.
See the 505 Service mode for defaulted communication constants and ranges. The 505 control supports
Modbus function code 4, which involves reading selected input registers. The input registers available are
listed in Table 6-8.
Analog Writes (Holding Registers)
Holding registers are analog values that are writable to the 505 control. These values can also be read
from by a device performing error checking. An example of an analog write value would be a direct speed
set point value as opposed to raise and lower commands. The value of the holding registers are also
stored in the control as numbers representing engineering units (psi or rpm). The 505 control supports
Modbus function codes 3, 6, and 16. These correspond to reading selected holding registers, writing to a
single holding register, and writing to multiple holding registers, respectively. The holding registers
available are listed in Table 6-8.
The following tables give the address and description of all Boolean and analog, reads and writes:
Table 6-7. Boolean Write Addresses
Addr Description Addr Description
0:0001 Emergency Shutdown 0:0056
Spare
0:0002 Emergency Shutdown Acknowledge 0:0057 Enable Extraction Control
0:0003 Controlled Shutdown 0:0058
Disable Extraction Control
0:0004 Abort Controlled Shutdown 0:0059
Lower Extraction Setpoint
0:0005 System Reset 0:0060
Raise Extraction Setpoint
0:0006 Start / Run 0:0061
Enable Remote Extr Setpoint Control
0:0007 Manual Open VLV Limiter 0:0062
Disable Remote Extr Setpoint Control
0:0008 Manual Close VLV Limiter 0:0063
Go To Modbus Entered Extraction Setpt
0:0009 Lower Speed Setpoint 0:0064
Open LP Valve Limiter
0:0010 Raise Speed Setpoint 0:0065 Close LP Valve Limiter
0:0011 Go To Rated (Idle / Rated) 0:0066
Decrease Extr/Adm Demand
0:0012 Go To Idle (Idle / Rated) 0:0067
Increase Extr/Adm Demand
0:0013 Halt Auto Start Seq 0:0068
Enable Extr/Adm Priority
0:0014 Continue Auto Start Seq 0:0069
Disable Extr/Adm Priority
0:0015 Enable Remote Speed Setpoint Control 0:0070
* Enable Droop Setpoint change
0:0016 Disable Remote Speed Setpoint Control 0:0071
* Disable Droop Setpoint change
0:0017 Go To Modbus Entered Speed Setpt 0:0072
* Enable Speed Fowarding
0:0018 Spare 0:0073 * Disable Speed Fowarding
0:0019 Arm Frequency Control 0:0074
0:0020 Disarm Frequency Control 0:0075
Momentarily Energize Relay 2
0:0021 Sync Enable 0:0076
Momentarily Energize Relay 3
0:0022 Sync Disable 0:0077
Momentarily Energize Relay 4
0:0023 Enable Cascade Control 0:0078
Momentarily Energize Relay 5
0:0024 Disable Cascade Control 0:0079
Momentarily Energize Relay 6
0:0025 Lower Cascade Setpoint 0:0080
Momentarily Energize Relay 7
0:0026 Raise Cascade Setpoint 0:0081 Enable Inlet Control
0:0027 Enable Remote Cascade Setpoint
Control 0:0082
Disable Inlet Control