Hitachi Sj7002 Owners Manual

Communications Reference Information
Appendix B
B–18
Communications Reference Information
Inverter
Affirmative ReplyThe standard affirmative reply from the inverter 
uses the ACK character (acknowledge) in the data 
field. The frame format of this reply follows the 
diagram and specification table.
Inverter
Negative ReplyThe standard negative reply from the inverter 
uses the NAK character (negative acknowl-
edge) in the data field. The frame format of 
this reply follows the diagram and specifica-
tion...

SJ7002 Inverter
Appendix B
B–19
Block Check 
Code (BCC)This section shows how the inverter protocol computes defines a BCC—block check code. The 
BCC is calculated for each frame transmitted and  can be used to verify the integrity of data 
transmission. The example below shows command  01 setting the inverter frequency to 5Hz.
The block check code is computed by using  the ASCII codes (shown above) and applying 
eXclusive OR (XOR) operations. Beginning with the  first pair of bytes, the result of their...

Communications Reference Information
Appendix B
B–20
Communication 
Test ModeThe communication test mode verifies that the inverter can properly send and receive data via 
the RS485 serial port. Follow the steps  below to perform the communication test.
1. Remove the serial cable (if pr esent) connected to the TM2 co nnector block of the control 
terminals, as shown below.
NOTE:  It is not necessary to connect a loopback ju mper. The RS485 port uses a transceiver for 
communications, which already allows...

SJ7002 Inverter
Appendix B
B–21
ModBus Mode Communications
Transmission 
ProcedureThe network master sends a frame to initiate communications with a slave, as shown in the 
figure below.
 Query - A frame sent from the external control equipment to the inverter
 Response - A frame returned from the inve rter to the external control equipment
 Wait time (C077) - If the inverter cannot complete the reception of a query from the host  (master)within the communicatio n timeout period, the inverter responds to...

ModBus Mode Communications
Appendix B
B–22
Message Config-
uration: QueryEach frame is formatted as follows:
Slave address:
 This is a numer from 1 to 32 assigned to each inverter (slave). (Only the inverter having the address given as a slave address in the query can receive the query.)
 When slave address “0” is specified, the query  can be addressed to all inverter simultane-
ously (broadcasting).
 In broadcasting, the host (master) cannot read  inverter data nor perform a loopback test.
Data:
 The...

SJ7002 Inverter
Appendix B
B–23
Header and trailer (silent interval):
Latency is the time between the reception of a query from the master and transmission of a 
response from the inverter.
 The header and trailer set the total time the  inverter should wait before sending a response 
after having received a query from the master system.
 Be sure to specify the time corresponding to the transmission of 3.5 characters (24 bits) as  the waiting time. If a shorter waiting time (co rresponding to the...

ModBus Mode Communications
Appendix B
B–24
No response occurs:
In the cases below, the inverter ignores a query and returns no response.
 When receiving a broadcasting query
 When detecting a transmission  error in reception of a query
 When the slave address set in the query is not equal to the slave address of the inverter
 When a time interval between data elements constituting a message is shorter than  3.5 characters
 When the data length of the query is invalid
NOTE: Provide a timer in the master...

SJ7002 Inverter
Appendix B
B–25
Explanation of 
Function CodesRead Coil Status [01h]:
This function reads the status (ON/OFF) of selected coils. An example follows below.
 Read intelligent input terminals [1] to [6]  of an inverter having a slave address “8.”
 This example assumes the intelligent input terminals have terminal states listed below  (coils 13 and 14 are OFF).
 The data set in the response shows  terminal states of coils 7 to 14.
 Data “17h = 00010111b” indicates the fo llowing assuming coil...

ModBus Mode Communications
Appendix B
B–26
Read Holding Register [03h]:
This function reads the contents of the specified number of consecutive holding registers (of 
specified register addresses) . An example follows below.
 Reading previous three trip factors from  an inverter having a slave address “5”
 This example assumes the previous  three trip factors are as follows:
The data set in the response is as follows:
When the Read Holding Register command cannot be executed normally, refer to the...

SJ7002 Inverter
Appendix B
B–27
Write in Coil [05h]:
This function writes data in a single coil. Coil status changes are as follows:
An example follows (note that to command the inverter, set A002=03):
 Sending a RUN command to an inverter having slave address “10”
 This example writes in coil number “1.”
When the Write in Coil command cannot be execut ed normally, refer to the exception response.
Write in Holding Register [06h]:
This function writes data in a specifie d holding register. An example...