Envision Peripherals manual Dynamic Ports, NV3128 RS-422A Machine-Control Data Switch

DYNAMIC PORTS

The power of the NV3128 as a data router begins with its singular ability to dynamically configure each of its 128 I/O ports to one of three states: controlling, controlled or high impedance. Executed automatically with each take command, this transparent changeover action in the router emulates the mode-swapping capability of the external machines. It simultaneously simplifies a system and expands its overall capability.

Fig. 1.4 illustrates this essential circuit function. Each I/O port presents a physical implementation of the standard RS-422A interface, to which a machine is connected without regard to data direction. Between the physical interface and the X-Y crosspoint matrix is a gated pair of RS-422A transceivers. Upon receipt of a Take command, the routers Control Card/Command Interpreter parses the incoming connection information and designates the port to which the source device is connected as controlled and the port to which the target is connected as controlling. It then sends this “state of the port” information to port controllers on the I/O modules. These port controllers, in turn, send gating signals to the transceiver pairs, turning the receivers and transmitters on or off appropriate to the direction of data flow. The valid port states are controlling , controlled, and controlling no response routed.

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NV3128 RS-422A Machine-Control Data Switch 1-9