MP200 and AC800PEC Modbus communication
As shown in attached picture, MP200 and AC 800PEC are connected to communicate via Modbus RTU interface as AC 800PEC is Modbus Master and MP200 is Slave type.
Initially, the Modbus Connection status shows 'Valid' in Master and connection gets disconnected (status 'Valid' goes to off) after Timeout period sets in Master. When we disconnect and reconnect the cable, the connection establish and breaks after Timeout period. And, when the Connection is 'Valid', we tried to read/write data between Master and Salve by using "MBWrite and MBRead" which gives error code -7011 in the MBRead and MBWrite function block.
DSCA 180B PROM firmware - 4911014-RYS, 4911014-RYT
DSPC 174 SW Version - SMPBAS SW*5.0/0, SMCUC SW 5.0/1
AC 800PEC - PPD 512 controller with FPGA version 126.96.36.199
HwdLibrary version - ModbusHwLib 2.11-4
Our doubts are,
1. As per the DSCA 180B PROM version, does it supports Modbus RTU protocol ?
2. As the connection shows 'Valid' the Hardwire conection and PORT configuration are okay. what are the other configuration settings to be verify for the problem ? (e.g Poll time, Pre-idle and TurnaroudTime etc.,)
3. Does this problem cause because Slave doesn't respond to Function-8 code from Master? It is mentioned in one of the Modbus manual that "Master sends Function-8 code to all configured Slaves and if the response is received with Function code-8 then a connection is established".
4. The Poll time set in MP200 slave is 12sec, but in 800PEC Master it can't be set more then 8sec and it set as 4sec. This can cause the problem ?
5. What is the alternative way to communicate with MP200 from AC 800PEC ?
does the DSPC 174 suports MB300 protocol ?
Voted best answer
The DSCA 180B will not act in Master mode unless the MP200 receives a response to a function code 8 from the slave. However, you say that the MP200 is a slave so this restriction should not apply.
The Modbus link is probably never on line - the AC800M just needs some time ( poll cycle time * no of retries) to detect that the link has failed. Poll time is not used by the slave. Are you sure you fully understand the Modbus settings in the MP200 controller and that it is properly configured as a slave ?
The communication lights on the front of the DSCA180B board should tell you if the board is receiving and transmitting messages.
To use MB300 the controller must be fitted with a DSCS140 communication board.
I dont recognize the software options you say the controller has. Can you post a screen shot of the initial connection message (including the software options) that you see when the MasterAid is first connected to the controller.