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Appendix E: Modbus Protocol
APPENDIX EModbus Protocol
Function 02 - Read Input Status
Address Word
0000 - 0001
Returns ok/alarm for each input queried. This is the current
input state, not the alarm status. It is one bit per input.
Function 04 - Read Input Registers
Address Word
0000 - 0028 Returns a 32 bit integer to represent the current input
value.
8 inputs, AC detect, and Battery level.
Function 03 - Read Holding Registers
Function 06 - Preset Holding Register
Function 10 - Preset Multiple Registers
Address Byte
01 System Parameters
00 Unit’s phone number 16 none
10 Dialing method 1 1:Tone 2:Pulse Tone
12 Voice reps 1 0 to 10 3
14 Callback acknowledge 1 1:Yes 0:No Yes
16 Max calling rounds 1 0 to 100 100
18 Rings till answer 1 1 to 20 1
1C Carrier wait time 1 0 to 60 sec 35