The MSU-6 is a device designed for sharing one RS232 link with multiple DTE devices. The composite or DCE port of the MSU-6 is typically accessed by RTS control. The MSU-6 can be modified to logically "OR" the 6 ports to the composite. The devices can be synchronous or asynchronous. The interface is RS232, up to 256 Kbps. All data from the composite, or common channel, is broadcast to all 6 ports. Data from the ports to the composite is sent only from the port that has asserted RTS and has received CTS back from the composite port. Ports are scanned at a sub-millisecond scan rate.
If more that 6 ports are needed, additional MSU-6s may be concatenated. Each additional MSU-6 adds 5 more ports, since one port is given up on the primary unit to support the addition of 5 more ports. Concatenating MSU-6 units adds virtually no delay to the system, as switching is done in less than a millisecond, even when concatenated several units deep.
The MSU-6 has active drivers and receivers on all ports. This insures that the unit exceeds the RS232 minimum cable distances. For example, the RS232 standard for 19,200 bps data is 50 feet of cable. With the active drivers and receivers, users often run cables in excess of 100 feet at 19,200 bps data rates.
When used as a synchronous device, the attached DCE device must be a source of clocking.
The MSU-6 has front panel LED's that show port activity for each port. On the composite, or common channel, there are LED's for Transmit Data, Receive Data and Clear to Send. There is also a power indicator.
The MSU-6 is normally used to share one DCE port amongst multiple DTE ports. To share a single DTE port amongst multpile DCE ports, such as broadcasting asynchronous data, see our Asynchronous Sharing Unit, the ASU. The ASU is available in 4, 8, 16, 24, and 32 port units. The data sheet is here.
