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NV3128 RS-422A Machine-Control Data Routing Switch 4-3

CHAPTER FOUR - THEORY OF OPERATION

4.1 SYSTEM

Fig 1.5 is repeated here to demonstrate the bidirectional flow of data through

the routing switch. The illustration shows a controlling machine sending and

receiving data through a controlled port on the router. Two crosspoints enable

the forward and reverse data paths through the switch. A controlled machine

receives and answers this command traffic through a controlling port.

4.1.1 CONTROL STRUCTURE

The Universal Control/Command Interpreter module receives commands

from an external control system and uses that information to pre-set an address

map of the entire crosspoint matrix. The address map is stored in double-

buffered RAM to prevent command updates from interfering with any take

activity in process. A programmable gate array transforms the address map into

the addresses and control commands that govern the operation of the crosspoint

modules. The mapping activity is continuous, with the Universal Control/

Command Interpreter module constantly pre-loading the crosspoints double-

buffered registers. At the take interval, a strobe pulse derived from the

reference input on the Universal Control/Command Interpreter module updates

the crosspoint registers with the pre-set information.

The Universal Control/Command Interpreter module additionally sends

information based on incoming commands to the I/O modules' on-board port

controllers. This data effectively causes one port to be configured as controlled,

and the other port in the route to be configured as controlling. The controlling

port will be associated with the source or destination parameter, depending on

the configuration of Reverse Src/Dest. See the explanation of Reverse Src/Dest

in the UniDiag manual for details.

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Envision Peripherals NV3128 Instrukcja Użytkownika Strona 65