Reznor GUARDIAN GB 1000, Installation Manual

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Reznor, Guardian 1 Phase Electric Heat with Signal Pro, Installation Manual, EN 2021-11, D301375 Iss 0 Page No 27
C
MODBUS Protocol
The modbus hardware is configured as follows:
• RS485 serial half-duplex interface
• 9600 baud
• 8 bits
• even parity / no parity (see below)
• 1 start bit
• 1 stop bit
• RTU mode
This means the same software will run in a standard
panel driven display and also in modbus mode, but
in a modbus installation only 8 maximum controllers
may be supported.
Modbus address – the unit will respond to it’s own
coded address as set by the bitswitches as follows: It
will also respond to ’broadcast’ mode 0.
Even parity settings
(Bitswitch3 OFF)
No parity settings
(Bitswitch3 ON)
Modbus
Address
Switch
Setting
Modbus
Address
Switch
Setting
16 0 24 8
17 1 25 9
18 2 26 A
19 3 27 B
20 4 28 C
21 5 29 D
22 6 30 E
23 7 31 F
Modbus function codes supported
Codes Descriptions
Range of
arguments
01, 02
Read coils, read discrete
inputs (equivalent)
Coils 1 to 24
03, 04
Read Holding registers,
input registers
(equivalent)
Registers 121 to
126
05 Write single coil Coils 13 to 24
06 Write single register Registers 125, 126
All other MODBUS function codes will generate
exception code 01, function not recognised.
Function arguments — Registers
0 Controller type Read only (undefined)
122
System control
temperature
Read only
123
Outside air
temperature
Read only
124 Power ratio Read only
125
Set point
temperature
Read/write
126
Set point
temperature on
door down
Read/write
(always to
nearest 5°C)
127 Hours run Read only (16 bit result)