©Copyright MAC Instruments 2005. All Rights Reserved. MAC155 Rev. 12
Pg 87
Modbus Input - Address Locations
7 6 5 4 3 2 1 0 = Address Location (Coil 1-8)
0x01 = 0 0 0 0 0 0 0 1 = Cancel
0x02 = 0 0 0 0 0 0 1 0 = Calibrate Request
0x04 = 0 0 0 0 0 1 0 0 = Calibration Check Request
0x08 = 0 0 0 0 1 0 0 0 = Maintenance Mode Request
0x10 = 0 0 0 1 0 0 0 0 = Force Output to 50%
Figure 67 - Modbus 8bit Input Word
To initiate modes the coils need to be forced for 10 seconds. Once a mode is
requested, the probe will remain in that mode until the cancel command is
received. The Calibration and Calibration check modes will return to Run mode
after the 22 minute calibration or calibration check process.
Controller Outputs
The MAC155 recognizes “Function 01 Read Coil Status”. This function
should be used to read the state of each address location. Compare the bit
pattern to the table following. The table represents address locations 17-24.
Modbus 8Bit Output Word
7 6 5 4 3 2 1 0 = Address Location (Coil 17-24)
0x00 = 0 0 0 0 0 0 0 0 = Run Relay OFF
0x01 = 0 0 0 0 0 0 0 1 = Run Relay ON
0x02 = 0 0 0 0 0 0 1 0 = Alarm Relay ON
0x04 = 0 0 0 0 0 1 0 0 = Moisture Error Relay
0x08 = 0 0 0 0 1 0 0 0 = Pressure Error Relay
0x10 = 0 0 0 1 0 0 0 0 = Low Water Alarm
0x20 = 0 0 1 0 0 0 0 0 = In Maintenance Mode
0x40 = 0 1 0 0 0 0 0 0 = In Warm-up Mode
Figure 68 - Modbus 8bit Output Word
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