Instruction Manual
Tek-LCD 7801C
www.tek-trol.com
Technology Solutions
100
10
Modbus RTU & ASCII Serial Communication
The controller is equipped with serial communication capability as a standard feature. Baud Rate,
Parity, Server ID (Address) and Transmit Delay are entered in the System menu, which appears in
the main Setup menu. The baud rate and parity selected must match the settings for all other
devices on the network. The Server ID must be unique, so it will not interfere with other devices.
Modbus Enron is supported by the Client/Snooper add
-on feature.
The controller supports the following Modbus functions:
Table 4: Modbus Functions
Command
Name
Description
01
Read Coils (0x)
Read coil value
03
Read Holding Register (4x)
Read multiple bytes from holding registers.
04
Read Input Register (3x)
Read multiple bytes from input registers.
05
Write Single Coil (Bit)
Set single coil value control
15
Write Multiple Coils (Bits)
Set multiple coil value control
06
Write Single Register
Set single value into specified holding register.
16
Write Multiple Registers
Set multiple values into specified holding
registers.
The multi-channel controller can also work as a “Modbus
Display/Controller” by writing the desired
value to the selected Modbus input (MB-1 to MB-199). The Modbus input can be used the same
way a 4-20 mA input is used; it can be brought into a channel to be displayed and generate alarms
to control relays, generate 4-20 mA outputs, and Modbus outputs (MO-1 to MO-64).
10.1
Modbus Register Tables
Table 5: Default Register Numbers / Addresses
Reg. Number
Reg. Address
Description
Data
Type
Function
Codes
R/W
40001
0
Channel (1) Value
Float
03, 04
R
40003
2
Channel (2) Value
Float
03, 04
R
40005
4
Channel (3) Value
Float
03, 04
R
40007
6
Channel (4) Value
Float
03, 04
R
40009
8
Channel (5) Value
Float
03, 04
R
40011
10
Channel (6) Value
Float
03, 04
R
40013
12
Channel (7) Value
Float
03, 04
R
40015
14
Channel (8) Value
Float
03, 04
R
40017
16
Total (1) Value
Float
03, 04
R
40019
18
Total (2) Value
Float
03, 04
R
40021
20
Total (3) Value
Float
03, 04
R
40023
22
Total (4) Value
Float
03, 04
R
40025
24
Timer (1) Value
Float
03, 04
R
40027
26
Timer (2) Value
Float
03, 04
R
40029
28
Timer (3) Value
Float
03, 04
R
