Q-214-236

FCTT
COMMUNICATION SPECIFICATION(Modbus RTU)

Q-214-236

Content

1. Communication specification ････････････････････････････････････････････

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2. Transmission and reception protocol ････････････････････････････････････

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3. Calculation method of CRC-16 ･･･････････････････････････････････････････

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4. Communication process flow chart ･･･････････････････････････････････････

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5. FCTT communication terminal arrangement ････････････････････････････････

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6. Modbus protocol RTU mode
6.1 Function code ･･･････････････････････････････････････････････････････

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6.2 Error response ･･････････････････････････････････････････････････････

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6.3 Measurement data request ････････････････････････････････････････････

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6.4 Model information request ･･･････････････････････････････････････････

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7. Communication monitor function ･････････････････････････････････････････

81Q-214-236

1. Communication specification
ItemSpecification

StandardTIA/EIA-485-A (2003)

Transmission system

Half-duplex two-wire system

Synchronous system

Asynchronous communication method

Bit rates

9600bps / 19200bps / 38400bps

Modulation code

NRZ

(The designation when ordering.)

Start bit

1 bit

Data length

8 bitsParityNone / Even number / Odd number

Stop bit

1 bit

Error detection

CRC-16 (X16＋X15＋X2＋1)

Connection method

M3 screw (FW11 socket) connection.

Cable length1000m (The total extension)(The designation when ordering.)

１

Address( )01 to 89（01H to 59H）and 00 (Communication is unused.)

Number of connections

Max. 64 sets (２) / One system

Transmission character

BinaryTransmission data are sent out from a bit 0.
Note(１) The setting change is made with a front switch.
The factory setting becomes an address 00 (communication is unused).
Note(２) When connection number connects 32 apparatuses, the number of the maximum connection decreases.
(to become the number of the connection of two sets in one)

2. Transmission and reception protocol(1) Normal request (Query).
The next WAIT is necessary by response.
9600bps：13 to 15ms
19200bps：11 to 13ms
38400bps：10 to 12ms

Master side

Address

Function
code

Data

CRC

Address

Function
code

Data

Slave (FCTT) side

Address

Function
code

CRC

Please do more than
3.5 character time.

(2) Timeout of between data.
Please make the interval of data and data into under 1.5 character time.
It becomes a timeout error if it becomes an interval more than 1.5 character time.
Please make the interval of data and data into under 1.5 character time.
9600bps：1.9ms or less.
19200bps：0.9ms or less.
38400bps：0.5ms or less.
Address

Function
code

DataCRC2

Q-214-236

3. Calculation method of CRC-16
CRC-16 is adopted as error checking in Modbus RTU mode.
An address, a function code, and data are calculated by the following method.
(1) Arithmetic process
CRC-16① 2 bytes of data-area X is secured to a CRC calculation.
② A default value (FFFFH) is substituted for ①.
Data X←FFFFH
Assignment③ XOR of data X and the nth data (n=1) is calculated.
It assigns for data X.
④ The 1-bit shift right of the data X is done.

Data X ←Date X XOR nth data

⑤ If carry occurs in operation of ④, data X and XORof A001H are taken.
⑥ Operation of ④ and ⑤ is repeated until it shifts
8 times.

Data X
Right 1 bit shift⑦ XOR of the next data (n+1) and Data X is calculated.
It assigns for Data X.
Carryoccurrence ?

NoYes⑧ Operation of ④ to ⑦ is repeated until processingof all data is completed.
Data X ←Data X XOR A001H⑨ 1 byte of high rank and 1 byte of low rank ofdata-area X for a CRC calculation are replaced.

(2) The example of calculation
No
8 times shiftend ？

CRC Object range
1 byte1 byte2 byte2 byte2 byteAddress

Function
code

Data address

Number ofrequest data

CRC

01H

04H

Yes

n+1

No
All data end？

Yes
The high order ofdata X, and lower
byte exchange

END

300H00H00H

19H

31C0H

Q-214-236

4. Communication process flow chart

Idle

Data receiving

No
Local address ？

YES

Error
Error check

NormalError
Function codecheck

NormalOut of rangeData-address
range check

NormalDatatransmission

Error codeanswer

5. FCTT communication terminal arrangement
Terminal No.
FCTT
1＋The termination resistor (100Ω) is connected byshort-circuiting a terminal 3(-) and a terminal
6(Ter.).
Please connect a termination resistor, if thisproduct is in the end (terminus) of communication
line.

3－4SG
100Ω
6RTer.

Inside common4

Q-214-236

6. Modbus protocol RTU mode
6.1 Function code
The next function code is supported with this product.

Function
codeName

Number of thedesignateddata

Data address

Master → FCTT

FCTT → MasterCommand message[Unit：byte]

Response message[Unit：byte]

Min.

Max.

Min.

Max.

04H

Measurement value data

30001 to 30125

Max. 125 words

88725503H

Model information

40501 to 40503

Max. 3 words

88711

6.2 Error response
In case the message transmitted from the master is judged to be error, this product does the next error
answer.
(1) In case it becomes a no-answer.
① In case a message transmission error occurs. (Overrun，Framing，Parity error，CRC)② In case the data interval of a message exceeds a regulation value (1.5 characters).
③ In case the message frame exceeding 8 bytes is received.
(2) In case of answer in error code.
In the error that does not correspond to (1), the following error response is returned.
At this case, the code that applied 80H to the code of a demand is returned to a function code.
And, the generated error code is returned as data.
1 byte1 byte1 byte2 byteAddress

Function code(+80H)

Error code

CRC01H

84H

02H

C2C1HError code list
Operation code

FunctionContents01H

Illegal function

The function cord a slave doesn't have was received.
(Function code which does not exist really)

02H

Illegal data address

The data address which is not defined as a slave is designated.
(Out of the address range)

03H

Illegal data value

The data more than the number of answer data are required.
Or the number of answer data to demand is 0 word.

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Q-214-236

6.3 Measurement data request
The measurement value of this product is read. There is no broadcast.
The function code designates 04H.
(1) Request of data (Query)
If a measurement value request is performed, it is necessary to designate the head address of data toacquire.
When sending the data address, please designate it by a relative address (30001 is subtracted fromthe address of the data address table.)
The number of data must designate the number of words of the data to request.
12Address

34

5Function Read start address
code(Relative address)

01H

04H

678

Number of data

CRC

0002H

71CBH

0000H

Data address list
Function code

Relative address

Data address

Contents of memory

Data type0000H

30001

INPUT 1 measurement value dataWORD0001H30002

INPUT 2 measurement value data

WORD

04

(2) Response
If measurement value request is performed normally, the following response will be returned from thisproduct side.
Example) Read start address：30001,

Number of data：2,

4

5

Measurement value data (INPUT 1,2)：10000

1

2

3

6

7

89Address

Function
codeAnswer
byte
count

INPUT 1
Measurement value
data

INPUT 2
Measurement value
data

CRC

01H

04H

04H

2710H

2710H

EAC9H

(3) Format of measurement value data (INPUT 1,2).
Input

Transmission data(hexadecimal)

Transmission data(Decimal)

Measurement range

0 to FULL (３)0H to 2710H

0 to 10000

0％ (４) and 120％ of input span.

D8F0H to 2710H±10000±FULL±120％ of input span.

３Note( ) 4‐20mA and 1‐5V input specification are included. (4‐20mA / 0‐10000, 1‐5V / 0‐10000)
Note(４) In the case of 4‐20mA, and 1‐5V input specification, a lower limit value is -25％ (about 0input) of an input span.

6

Q-214-236

6.4 Model information request
The type code of this product is read. There is no broadcast.

The function code designates 03H.

(1) Request of data (Query)
If a model information request is performed, it is necessary to designate the head address of data toacquire.
When sending the data address, please subtract 40001 from the address of a data address table.
The number of data must designate the number of the data to request.
123

4

5

678Address

Function
code

Data address

Number of data

CRC

01H

03H

01F4H

0001H

C404H

Data address list
Function code

03H

Relative address

Data address

01F4H

40501

Model information, Type code

Contents of memory

01F5H

40502

Not used (0000H)

01F6H40503

Not used (0000H)(2) Response
If model information request is performed normally, the following response will be returned from thisproduct side.
12

3

4

56Address

FunctioncodeAnswerbytecount

Type code

CRC

01H

03H

02H

0020H

B99CH

Model information, Type code
Type

Communication data

FCTT

0020H

77

Q-214-236

7. Communication monitor function
This function is valid only at the case of communication use.
Communication status is distinguished in the state of lights of RUN LED.
The communication monitor function doesn't operate on address 00 and at 90 to 99 (Communication is unused).
(RUN LED will be the lights.)
The monitor specification will be below.

Communication monitor

Status ofcommunication

Definition
Status of RUN LED

Priority

NormalThere is communication to local. And whenreplied with normalcy by error detecting.
Return from abnormal state becomes reset
automatically.

Always lights.
(The address always also
lights at 00 and 90 to 99.)

3Error・Time-out.
・Transmission error (Parity error /Overrun error / Framing error), CRC error

The flicker in a cycle of0.5 seconds.

1(Top priority)

Other

Setting error relation.
・Communication address is changed during
power supply applying. (Operation by thecommunication address before change.)

The flicker in a cycle of
1 second.

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Q-214-236

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DATE：December 9, 20149