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MP 2008\2208
Appendix B - Cable Specifications

RS-232 Cables

The Cubix MP package includes an "octopus" shielded cable that converts the 78-pin high density connector on the adapter to eight DB-25 male RS-232 D-connectors. All ports are wired as the DTE interface. The pin-outs for the RS-232 connections are standard:

1 Chassis Ground
2 Transmit Data (TxD) output
3 Receive Data (RxD) input
4 Request To Send (RTS) output
5 Clear To Send (CTS) input
6 Data Set Ready (DSR) input
7 Signal Ground (GND)
8 Data Carrier Detect (DCD) input
20 Data Terminal Ready (DTR) output
22 Ring Indicator (RI) input

Connection to Modems

The Octopus Cable shipped with the MP 2x08 adapter connects the MP adapter to external modems. If distances greater than the length of the octopus cable must be accommodated, an additional "straight-through" cable may be connected to the octopus cable’s DB-25 RS-232 D-connector then to the modem.

At a minimum, connections should be provided on the pins noted in the RS-232 Cables section above. Connections on all 25 pins are acceptable.

Connection to Hosts, Workstations, PCS, or Terminals

Direct connection of the MP adapter’s RS-232 ports to hosts, workstations, PCS, or terminals configured as DTE equipment (without an intermediate modem or DCE device) generally requires a "null modem" cable. A "null modem" cable eliminates the need for modems (DCE devices) by crossing RS-232 signal pairs between the two DTE devices, such that each appears to the other as a DCE device.

To connect the MP adapter to another DTE device, connect the octopus cable’s 78-pin connector to the MP adapter. Connect the "null-modem" cable (described below) to one of the octopus cable’s DB-25 RS-232 D-connectors then connect the null modem cable directly to the DTE device.

To make a "null-modem" cable, use the following connections:

MP Series Board Other DTE Side

	   2 --------------------- 3
	3 --------------------- 2
	4 --------------------- 5
	5 --------------------- 4
	7 --------------------- 7
	6 -----|-------------- 20
	8 -----|
	20 -------------|------ 6
	                 |------ 8

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