7200MA
RS-485 MODBUS Communication
Application Manual
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7200MA MODBUS MANUAL.DOC
7200MA MODBUS Application Notes 
1. Brief Introduction
This manual describes the communication methods
between TECO frequency inverter 7200MA and host controllers(PC,PLC…).
2. Software Standard
cUsing RS-485 Interface
dMODBUS RTU mode protocol
eCommunication Format (Setting by Inverter‘s parameter)
Transfer Speed 1200/2400/4800/9600 bps (Setting by parameter Sn-37)
Parity no parity/even parity/odd parity (Setting by parameter Sn-38)
3. Wiring Terminal
7200 MA
S(+)
S( - ) RS-485
Interface
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7200MA MODBUS Application Notes 
4. Related parameters for MODBUS communication
(1) |
Node address |
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Sn-36 |
=1~31 ------------------------- |
Inverter Node address (Default = 1) |
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(2) |
Transfer Speed (baud rate) |
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Sn-37 |
= 0------------------------------ |
1200 Bps |
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= 1------------------------------ |
2400 Bps (Default = 1) |
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= 2------------------------------ |
4800 Bps |
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= 3------------------------------ |
9600 Bps |
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(3) |
Data Parity |
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Sn-38 |
= 0------------------------------ |
No Parity (Default = 0) |
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= 1------------------------------ |
Even Parity |
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= 2------------------------------ |
Odd Parity |
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(4) |
Stopping method while RS485 Communication Fault |
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Sn-39 |
= 0------------------------------ |
Decelerating to stop by Bn-02 |
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(Default = 0) |
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= 1------------------------------ |
Coasting to stop |
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= 2------------------------------ |
Decelerating to stop by Bn-04 |
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= 3------------------------------ |
Continuous operation |
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(Can be stop by |
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Key) |
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STOP |
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(5) Time-out Check |
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Cn-27 |
= 00.0 s ----------------------- |
Don‘t care |
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= 01.0 s ----------------------- |
Checked error (Default = 01.0 s) |
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7200MA MODBUS Application Notes 
5.Inverter connected with host controller
(1)Operation procedure
cInverter power turn on Set the related parameters dConnect inverter and host controller
eHost controller sends communication message
(2)Communication status indication of inverter
We can set the Run/Stop command (Sn-04) or Frequency Reference (Sn-05) by RS485. Inverter will display “Alarm RS-485” if it does not receive any message from host controller after power on 5 seconds. This display will disappear while inverter had received messages from host controller.
We can set Time-out Check. Inverter will display “Alarm RS-485” if it does not receive any message in Time-out (Cn-27).
Parameter Sn-39 will decide the “Alarm RS-485” display format. Sn-39 = 0 Decelerate to stop by Bn-02 (“Alarm RS-485” light up)
=1 Coasting to stop (“Alarm RS-485” light up)
=2 Decelerate to stop by Bn-04 (“Alarm RS-485” light up)
=3 Continuous operation (“Alarm RS-485” flash)
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7200MA MODBUS Application Notes 
6.Description of MODBUS communication
(1)In MODBUS RTU mode protocol one message has 4 parts include Slave Address Function Code Data and CRC-16 Character.
The interval between two messages needs 3.5 characters transferring time.
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T1 T2 T3 T4 |
Slave |
Function |
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Data |
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CRC-16 |
T1 T2 T3 T4 |
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Address |
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Character |
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T1~T4 3.5 characters transferring time at least |
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(2)Data bit format for MODBUS RTU mode |
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Even/Odd Parity |
start |
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parity |
stop |
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No Parity |
start |
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stop |
stop |
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(3)Slave Address
Parameter Sn-36 can set the node address of each inverter (1~31). Every slave stand can receive the message sent from host controller. Only the corresponding one returns the message to master.
IF the slave address of receiving message is 0, all slave stands will execute this command but do not return the message to master.
This message can only use for Run/Stop, Fault Reset (Address 0000H) and Frequency Reference (Address 0001H).
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7200MA MODBUS Application Notes 
(4) Function Code
Code |
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Remark |
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03H |
Read Data from Holding Register |
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08H |
Loop Test |
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10H |
Write Data to Holding Register |
slave address can be 0 |
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(5) Data Character
Detail descriptions will be discuss later because it depends on different Function Code.
(6) CRC-16 Character(16-bit binary value) CRC-16 Generation Procedure
c Load a 16-bit register with 0xFFFF. Call this the CRC register.
d Exclusive OR the first 8-bit byte of the message with the low order byte of the 16-bit CRC register, putting the result in the CRC register.
e Shift the CRC register one bit to the right(toward the LSB), zero filling the MSB. Extract and examine the LSB.
f If the LSB is 0, repeat Stepe(another shift). If the LSB is 1, Exclusive OR the CRC register with the polynomial value 0xA001.
g Repeat Stepeand Stepfuntil eight shifts have been performed. When this is done, a complete 8-bit byte will have been processed.
hRepeat Stepd gfor the next 8-bit byte of the message. Continue doing this until all bytes have been processed. The final result of the CRC register is the CRC value.
iWhen the CRC is placed into the message, its upper and lower bytes must be swapped.
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7200MA MODBUS Application Notes 
(7)Inverter return messages
c Please refer to the “Message Format” in next page about inverter returning messages for more detail descriptions.
dIt needs 5ms to return messages after inverter had received normal message from host controller.
eIn next two cases, inverter does not return any message
z There are any error detection in received data message (parity error, framing error, overrun error or CRC-16 error).
zSlave Address character is different to parameter Sn-36 (Inverter Slave No.).
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7200MA MODBUS Application Notes 
7. Message Format
7200MA supports 3 MODBUS Function Codes only.
Table1 Message Length
Function |
Code |
Description |
Host Query |
Inverter Return |
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Byte |
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Byte |
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(Min.) |
(Max.) |
(Min.) |
(Max.) |
Data Read |
03H |
Read Data from Holding Register |
8 |
8 |
7 |
37 |
Loop Test |
08H |
Loop Test |
8 |
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8 |
8 |
Data Write |
10H |
Write Data to Holding Register |
11 |
41 |
8 |
8 |
(1) Read Holding Register Command(Item 8:Holding Register Tag List)
Host Query |
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Inverter Return(Normal) |
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Slave Address |
01H |
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Slave Address |
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01H |
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Function Code |
03H |
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Function Code |
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03H |
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Head Address |
High Byte |
00H |
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Data Byte Count |
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02H |
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Low Byte |
00H |
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High Byte |
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00H |
Access Count |
High Byte |
00H |
(*1) |
Data Value |
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Low Byte |
01H |
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Low Byte |
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00H |
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Low Byte |
84H |
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CRC-16 |
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CRC-16 |
Low Byte |
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B8H |
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High Byte |
0AH |
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High Byte |
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44H |
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Inverter Return(Error Detected)
Slave Address |
01H |
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80H+Function Code |
83H |
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Error Code |
03H |
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CRC-16 |
Low Byte |
01H |
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High Byte |
31H |
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*1 Host controller can read 16 registers at most in each transferring message.
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7200MA MODBUS Application Notes 
(2) Loop Test Command(Test inverter communication status)
Host Query |
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Inverter Return(Normal) |
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Slave Address |
01H |
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Slave Address |
01H |
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Function Code |
08H |
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Function Code |
08H |
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High Byte |
00H |
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Test Code |
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Test Code |
High Byte |
00H |
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Low Byte |
00H |
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(*1) |
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Low Byte |
00H |
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High Byte |
AAH |
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Test Data |
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Test Data |
High Byte |
AAH |
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Low Byte |
55H |
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Low Byte |
55H |
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Low Byte |
5EH |
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CRC-16 |
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CRC-16 |
Low Byte |
5EH |
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High Byte |
94H |
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High Byte |
94H |
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Inverter Return(Error Detected) |
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*1 Test Data can be any random value. |
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Slave Address |
01H |
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80H+Function Code |
88H |
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Error Code |
01H |
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CRC-16 |
Low Byte |
87H |
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High Byte |
C0H |
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