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LIST OF MODBUS REGISTERS (LCT-485 REGISTERS)
Address
R/W
0xD0 (208)
R/W
0xD1 (209)
R/W
0xD2 (210)
R/W
0xD3 (211)
R/W
0xD4 (212)
R/W
0xD5 (213)
-
0xD6 (214)
R/W
* If changed, the new value will only take effect after power is cycled, or after "1" is written to
Function Register 0xD6
** Mode "2": after detecting the baud rate, the LCT-485 then selects the nearest "known" baud
rate from the following common values: 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400,
57600 (see "Automatic Bus Configuration Mode" below)
Notes
1.
All temperatures are in tenths of degrees C
2.
All write operations are saved to non-volatile memory
3.
For further information please refer to
4.
Use address 255 to communicate with any connected LCT-485 unit sensor (ensure only
one LCT-485 unit is connected)
5.
Use address 0 to broadcast to all connected LCT-485 units (no response expected)
AUTOMATIC BUS CONFIGURATION (ABC) MODE
The LCT-485 can automatically detect the correct baud rate, parity and stop bit settings used
by the Modbus Master. This mode is enabled by default. To use ABC mode:
1.
Configure the Modbus Master to repeatedly send Read messages to the LCT-485.
Ensure the timeout period of the Modbus Master is no shorter than the LCT-485 unit's
reply delay (1 second). Ensure the Modbus Master will continue to try to send messages
after many timeouts.
2.
The LCT-485 will listen for messages from the Modbus Master. At first it will use the
chosen settings for baud rate, stop bits and parity. If none of these settings have been
configured, the default values will be used.
3.
After several failed messages, if the chosen settings do not work, the LCT-485 will
automatically measure and set the baud rate. It will then try all the possible
combinations of stop bit and parity settings until it finds the correct values.
4.
The LCT-485 will detect when good communications with the Modbus Master have been
established, and ABC mode will then be completed. The automatically-detected values
will be stored in the LCT-485's Modbus registers. ABC mode will not begin again until the
power is cycled.
5.
It is possible to change the baud rate, parity and stop bit settings by writing to the
Modbus registers. The LCT-485 will use the new settings after the power is cycled, or
after "1" is written to Function Register 0xD6.
RECOVERY MODE
In the event that the settings for parity, stop bits and baud rate are lost or unknown, and ABC
mode is "0" (Off), communications can be restored as follows:
Configure the Modbus Master to repeatedly send Read messages using 9600 baud, no parity,
1 stop bit. After several messages, the LCT-485 will temporarily revert to these settings until
the power is cycled. This will allow the original correct settings to be read from the LCT-485.
These recovery settings are not stored, and they do not overwrite the existing settings.
Description
Modbus slave address*
Baud rate*
Parity (0 = none, 1 = odd, 2 = even)*
Stop bits
(1 = 1 stop bit, 2 = 2 stop bits)*
Automatic bus configuration (ABC)
mode
(0 = off, 1 = on, 2 = on using nearest
known baud rate**)
[RESERVED]
Function register
(1=reload, 0x5555=factory reset)
Cleared automatically
http://www.modbus.org/specs.php
Default
Min.
value
value
1
1
9600
400
0
0
0
0
1
0
-
-
0
0
Max.
value
247
60000
2
1
2
-
65535
7
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