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Appendix A
RS485 Port Usage For Serial Modbus RTU protocol:
The Modbus option on the fire pump controller boards can be enabled by disabling the printer option to the onboard RS485 port.
All communications to this port will be in a 2 wire RS485 format. 255 controllers can communicate on a single network. The
pinout cabling required for connection to the port is as follows. It is necessary to apply a terminating resistor to both ends of the
network. Note-Only 50 Modbus registers can be polled at time from the controller. I/O servers must be set up accordingly.
Modbus Setup From Controller Interface:
From the 200 series user preference configuration screens the Modbus setting can be access from screens 220 through 223. Screen
220 is used to set the Modbus address 1-255. All Modbus devices on a network must have a unique address.
Screen 221 is used to enable/disable the Modbus option. If ‘Yes’ is selected the Modbus will be enabled and the RS485 port can
no longer be used as a printer port.
Screen 222 is used to set the baud rate for the RS485 port. The baud rates possible are 2400, 4800, 9600, 19200, and 38400
bits/second. Note that the baud rate setting is for the RS485 port in general and applies for Modbus and printer usage.
Screen 223 is used to set the Modbus parity. Valid selections are ‘Even’, ‘Odd’, and ‘None’. This setting must match the parity
setting of all other Modbus devices on the network.
Modbus Register Usage Description:
The historical event and pressure logs, and real time clock can be accessed and controlled through the Modbus registers listed
below.
Register 40001 is a write to controller only register where commands can be entered to accomplish the following as seen in figure
1.1. Depending on the Modbus I/O server used, either the individual bits in register 40001 can be toggled or integer values can be
written. Either way, the controller automatically zeros register 40001 after a valid command is received.
Figure 1.1
Description
Modbus Registers
Usage Notes For Read/Write Registers
Set Real Time Clock
040001:0
Bit 0 Of Modbus Register 040001 - Must Write a 1 Into Register 040001 To Set Clock
Remote Start Diesel Engine
040001:1
Bit 1 Of Modbus Register 040001 - Must Write a 2 Into Register 040001 To Start Engine
040001:2
Increment Event Historical Log Data
040001:3
Bit 3 Of Modbus Register 040001 - Must Write an 8 Into Register 040001 To Increment Event Historical Log Pointer
Decrement Event Historical Log Data
040001:4
Bit 4 Of Modbus Register 040001 - Must Write a 16 Into Register 040001 To Decrement Event Historical Log Pointer
Increment PSI Historical Log Data
040001:5
Bit 5 Of Modbus Register 040001 - Must Write a 32 Into Register 040001 To Increment PSI Historical Log Pointer
Decrement PSI Historical Log Data
040001:6
Bit 6 Of Modbus Register 040001 - Must Write a 64 Into Register 040001 To Decrement PSI Historical Log Pointer
Set Historical Event Log To Most Current Record
040001:7
Bit 7 Of Modbus Register 040001 - Must Write a 128 Into Register 040001 To Set Event Historical Log To Most Current Record
Set Historical PSI Log To Most Current Record
040001:8
Bit 8 Of Modbus Register 040001 - Must Write a 256 Into Register 040001 To Set PSI Historical Log To Most Current Record
