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stratok

PC - modem - modem - PLC

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hi, i'm trying to communicate whit a CJ1M PLC with a Java class. If i connect PC and PLC directly witch a serial cable,then the communication works fine and i can send hostlink commands and receive hostlink response from the PLC. The problem is: if i try "to use" a modem communication, i can send AT commands to the local modem to call the remote modem, when the connection is established i try to send hostlink commands but i don't receive nothing. If i try to use a PC connected to the remote modem and i look at the frames coming in, i can see only unknown characters (squares etc.). But if i send the AT command to the remote modem whit the hyperterminal before the local modem try the connection, then i can see the correct characters and then i can connect the remote modem to the PLC (whitout turning off the modem) and send and receive hostlink commands correctly. Wath can i do? Can anyone help me? Does exist an AT command to configure the remote modem? Thank you in advance PS: sorry for my english

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Try another modem perhaps ? We always use Westermo modem on PLC side and they work great. Everything can be set by dipswitches so no AT settings necessary. Have a look at the attached manual. TD_32B.pdf

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Here's an example pinout for the cable between TD32B Modem - PLC.

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make sure you connect a 9600 (Master pc) to modem(internal or external ) 9600 modem to modem ( 9600) and modem to Hostlink 9600 with no compression it is the fastest you can go wich At command do you talk about AT????? .... because the remote modem should be ready for answer so don't need any At command but if you send a command other than answer this mean that you send configuration to this modem maybe that>s why it work so what you can do is save this config to the default in the flash or memory and restore it each time it's booting ( the remote modem)

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We used also remote connection to PLC via telephone line. Not any more 'cause during heavy thunder, lightning hit the telephone line => modem, plc and pc totally kaput. Next time I'll use protected telephone plugs.

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Some modems require AT commands to switch communication mode to digital communication. It is better to find a AT Command manual of your modem.

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