EAGLE CONTROLLER – INSTALLATION & COMMISSIONING INSTRUCTIONS
EN1Z-0970GE51 R0918 10
Table 6. Baud rate vs. max. cable length for RS485
Baud rate Max. cable length (L)
9.6 - 76.8 kbps 1200 m
*115.2 kbps 1000 m
* In the case of configuration of RS485-2 for Panel Bus, the
communication rate is set to 115.2 kbps.
For information on wire gauge, max. permissible cable length,
possible shielding and grounding requirements, and the max.
number of devices which can be connected to a bus, refer to
standard EIA-485.
Modbus Connection
The EAGLE controller can function as a Modbus Master.
In general, the RS485 wiring rules must be followed.
Wiring Topology
Only daisy-chain wiring topology is allowed.
MODBUS
MASTER
MODBUS
SLAVE
MODBUS
SLAVE
MODBUS
SLAVE
MODBUS
SLAVE
Fig. 16. Allowed Modbus wiring topology
Other wiring topologies (e.g., star wiring, or mixed star wiring
and daisy chain wiring) are prohibited; this is to avoid com-
munication problems of the physical layer.
MODBUS
MASTER
MODBUS
SLAVE
MODBUS
SLAVE
MODBUS
SLAVE
MODBUS
SLAVE
MODBUS
SLAVE
MODBUS
SLAVE
Fig. 17. Prohibited Modbus wiring topology (example)
Cables
See also section "EIA 485 Cable Specifications" on pg. 26.
Use shielded twisted pair cable J-Y-(St)-Y 2 x 2 x 0,8.
You must use three wires:
One wire for D1 = Modbus +
One wire for D0 = Modbus –
One wire for the signal common
When using one pair for D1 and D0 and one wire of another
pair for the signal common, CAT5 cable may also be used.
For connection details, see section "Modbus Connection" on
pg. 31.
Shielding
Shielding is especially recommended when the Modbus cable
is installed in areas with expected or actual electromagnetic
noise. Avoiding such areas is to be preferred.
Use shielded twisted pair cable shielded twisted pair cable J-
Y-(St)-Y 2 x 2 x 0,8 and connect the Modbus to a noise-free
earth ground – only once per Modbus connection.
RS485 Repeaters
RS485 repeaters are possible, but have not been tested by
Honeywell. Hence it is within responsibility of the
installing/commissioning person to ensure proper function.
NOTE: Each Modbus segment will require its own line
polarization and line termination.
Modbus Master Specifications
Modbus Compliance
As per the Modbus standard, the EAGLE controller is a con-
ditionally compliant "regular" Modbus device.
The EAGLE controller differs from an unconditionally com-
pliant "regular" Modbus device in that it does not support
communication rates of 1.2, 2.4, and 4.8 kBaud (because
these communication rates are not market-relevant).
Physical Layer
2-wire serial line RS485 (EIA-485) (with additional common)
Communication rates: 9.6, 19.2, 38.4, 57.6, 76.8, and
115.2 kBaud supported.
Max. number of devices: 32
Cable and wiring specifications: See section "Wiring and Set-
Up" on pg. 14.
Communication Mode
Modbus Master.
Transmission Mode
RTU (Remote Terminal Unit)
Address Range
Modbus slaves can have an address between 1 and 247.
Discrete Inputs, Coils, Input Registers and Holding Registers
can have an address between 1 and 65534.
Function Codes
The following function codes are supported:
Table 7. Supported function codes
function code (hex) function
02 Read Discrete Inputs
01 Read Coils
05 Write Single Coil
04 Read Input Register
03 Read Holding Register
06 Write Single Register
10 Write Multiple Registers
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