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DLM4000 User Guide
PN 161-09997-003A
Feb 2005
When communicating between two PLCs, I have a flashing T LED on the Master and a flashing R LED on the
Remote. I never have a flashing R on the Master and T on the Remote.
1. The poll is getting to the remote PLC, but it is not answering back. Verify that the PLC addressing is correct.
2. If possible, try connecting the PLCs together with a null cable directly. If they do not work, most likely a PLC
programming or processor issue exists.
3. Make sure that no handshaking is used in the PLC.
4. Check and verify that the word length is 10bits and the baud rates match. Verify this on both PLC locations.
5. Make sure the protocol is asynchronous and not synchronous.
6. Verify that the cabling is correct.
After a storm the DLM4000 modem is not longer operating.
1. Verify that surge protection is not damaged.
2. Re-initialize modem configurations.
3. Verify DLM4000 operation with a bench test.
4. Verify that DLM4000 power supplies are still operating properly.
I cannot locate a software driver for the DLM4000 modem.
No driver is necessary for the DLM4000 modem. We configure the modem for the application ahead of time. Industrial
software and logic controllers may offer additional configuration options, but no software driver is required. The DLM4000
modem is not designed or intended for providing Internet access.
I am trying to dial with the DLM4000, but the modem keeps disconnecting before establishing a carrier.
1. Ensure that the equipment connected to the dialing modem is not sending data into the DLM4000’s serial port. Any
data sent into the modem in dial mode is viewed as a command and the dial sequence will be terminated. If it is not
possible to discontinue the transmission of data, contact Data-Linc Group for help.
2. Verify that the modems can connect locally to each other. A possible line problem may exist.
3. Make sure the configuration of both of the DLM4000 modems matches per the configuration sheet.
