Eaton Power Xpert PXM 4000, User And Installation Manual

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8 Setup on the Web Server Pages
the performance of the Display Link. Modbus modes 3 and 4 allow you to automatically split the
requests between the the two ports, depending on the slave device address. These are “load
balancing” options as all Display Link address fall in the lower part of the range, and are therefore
automatically routed to a particular RS485 port using these modes.
Modbus Timeouts
The following explains the Modbus timeout settings, and how to use them. These two settings com-
bine to create a total timeout period (in ms) that equals the following formula:
Total Timeout = Subnet Timeout X (Subnet Retries value + 1)
If a subnet device doesn’t respond within the Total Timeout, the meter responds with exception 11
(0xb) or “Gateway Target Device Failed to Respond.”
Subnet Timeout This is the timeout value (or amount of time permitted for a subnet device to
respond to a command). The default value is 1000 ms. This can also be set via
Modbus register 2005.
Subnet Retries The number of times the meter will retry a subnet command before issuing. The
default value is 0 (or, “only try once”).
Modbus Subnet Gateway Configuration
The Subnet Mode field controls how the meter behaves as a Modbus subnet gateway. See page
6A-25 for instructions on configuring the RS485 ports (COM1, or if the Communications Adapter is
installed, COM2.)
0
Setting the Subnet Mode to zero disables the meter from functioning as a Subnet Gateway
Master. It will only respond to Modbus commands sent to its own slave address. The local ad-
dress is the base address set by the hex switch.
1 This is the default setting for COM1
. Setting Subnet Mode to 1 enables the meter as a
Modbus Subnet Gateway Master. This is the default setting for Com1The meter will route any
commands to slave addresses (other than its own) to the RS485/RS-232 port set as a Master-
Gateway. If no response is received from the slave device within the total timeout (specified
above), the meter returns an exception 11 (0xB) “Gateway Target Device Failed to Respond.”
If no RS-485 port is currently set as the Master-Gateway, the meter returns an exception 10
(0xA) “Gateway Path Unavailable.”
2 This is the default setting for Com2. Setting the mode to 2 also enables the meter as a
Modbus Subnet Gateway Master. This is the default setting for Com2. The meter will route any
commands to slave addresses (other than its own) to the RS485/RS232 port set as a Master-
IO. If no response is received from the slave device within the total timeout (specified above),
the meter returns an exception 11 (0xB) “Gateway Target Device Failed to Respond.” If no
RS485/RS232 port is currently set as the Master-IO, the meter returns an exception 10 (0xA)
“Gateway Path Unavailable.”
3 This is a load balancing option that requires that the optional Communications Expansion card
has been installed. Unlike Subnet Gateway Master modes 1 and 2, the Gateway will route any
commands to slave address (other than its own) to one of the RS485/RS232 ports, depending
on the address. Slave addresses of 127 or below are routed to the RS485 port configured as a
Master-IO while slave addresses of 128 or above are routed to the Master -Gateway.
As with the other Subnet Gateway Master Modes, if no response is received from the slave
device within the total timeout (specified above), the meter returns an exception 11 (0xB)
“Gateway Target Device Failed to Respond.” If no RS-485 or RS232 port is currently set as
either the Master-Gateway or Master-IO, the meter returns an exception 10 (0xA) “Gateway
Path Unavailable.”
4 This is another “load balancing” option that requires that the optional Communications Expan-
sion card has been installed. The Gateway will route any commands to slave address (other
than its own) to one of the RS485 or RS232 ports, depending on the address. Slave addresses