DEC MMJ Serial

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Image:connector_mmjf.png 6 pin MMJ female connector at the devices.

Image:connector_mmjm.png 6 pin MMJ male connector at the cables.

Pin Name Description
1 DTR Data Terminal Ready
2 TXD+ Transmit Data +
3 TXD- Transmit Data -
4 RXD- Receive Data -
5 RXD+ Receive Data +
6 DSR Data Set Ready


A common task is to build an adaptor to RS-232 using the DB-25 or DE-9 plug on the one side (to be connected to a PC) and the MMJ connector on the other. Though serial transmission is done with differential voltage, it’s actually quite easy. Simply connect MMJ pins 3 and 4 to the DB-25 / DE-9 GND pin, then use MMJ pins 2 and 5 as regular TX/RX pins (to be connected to pins 2 and 3 on the DB-25 / DE-9 side, depending on whether to build a direct crossed console cable or just an adaptor. You can also connect pins 1 and 6, but I’m not exactly sure where. For a plain console cable, they are not necessarily needed.


Category:Serial Connectors


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