Envision Peripherals NV3128 User Manual download pdf (Page 19)

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

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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Envision Peripherals NV3128 User Manual Page 19