Components AS-Interface

1 components

1.1 scanners , gateways
1.2 power supply
1.3 modules
1.4 network cable

components

an as-interface network requires few basic components falling following general categories:

scanners / gateways (also called masters)
power supplies , repeaters
modules (also called slaves)
network cable, installation hardware , useful tool (infrastructure)

scanners , gateways

the scanner/gateway performs 2 functions. respect as-interface network master, performing data exchange modules , updating internal i/o image. functionality of master defined in master profile of as-interface specification. part of specification version 3.0 m4 master profile has been defined. given network can have 1 scanner/gateway. respect connected plc/dcs or pc scanner/gateway slave. as-interface community typically uses word gateway when as-interface master connects upper-level network devicenet, profibus or of industrial ethernet flavors. on other hand, if resides on backplane of plc referred scanner. since as-interface communication based on master-slave communication method, network must have 1 master @ time.

power supply

any as-interface segment must powered. typically accomplished connecting as-interface power supply. these supplies have unique characteristics regarding internal circuitry , output voltage. standard 24 v dc power supplies cannot used directly power segment, 31.5 v dc must used instead. total length as-interface network cable in single segment must no more 100 m. if total network length must longer, repeaters can used. repeater galvanically isolates 2 segments, new power supply must used on far side of repeater. common misconception exists concerning number of repeaters in network. has been stated maximum length of as-interface network can 300 m, created using 2 repeaters. not case. matters not how many repeaters using rather how many repeaters data packet, originating @ scanner or gateway, has cross before reaching i/o node. due tight timing constraints defined each packet can @ travel across 2 repeaters before reaching as-interface node. has following consequences:

modules

this far largest group of components , includes binary , analog i/o modules, stack lights, push buttons, sensors integrated asic, valve control boxes, e-stops, light curtains; in general device can exchange data plc. each module on network must have unique address. as-interface address space ranges 0 31, 0 cannot used, reserved automatic single node replacement. since adoption of specification 2.11 address space further divided , b extended addresses. result, using module designed support addressing mode, possible have 2 modules @ each address; 1 @ half , 1 @ b half. (ex. 1a , 1b, 17a , 17b)

the current specification version 3.0 has added ability construct many new types of i/o combinations, including binary modules 4 inputs , 4 outputs supporting a/b addressing.

network cable

the vast majority of as-interface installations utilize as-interface flat cable, defined part of as-interface specifications. relatively small number of industries (e.g. valve control in process automation) use round cable, because easier pull through conduit. while shape of cable not matter (any other cable can used) electrical characteristics of selected cable matters greatly. prevent problems due improper cable, professionals suggest as-interface flat cable. cable designed make use of cable piercing technology. when as-interface module installed on network, piercing needles penetrate cable jacket , displace internal copper strands without cutting them. allows as-interface modules installed anywhere on network without cutting , preparing (i.e. removing cable jacket, stripping insulation , possibly applying ferule) cable first. result faster installation without chance of inadvertent shorts between leads.

there several types of cables available. yellow cable used power as-interface modules , enable communication between field devices , scanner or gateway. cable offered in several jacket materials address specific applications needs. as-interface black cable typically used supply modules 24 v dc aux power. no communication takes place on cable. similar yellow cable, black cable produced using various jacket material address specific needs of application. red-jacketed cable has been defined virtually unused. intended use in applications ac power supplied field nodes. 2 leads inside as-interface cable brown (+ lead) , blue (− lead) independent of material makeup , outer jacket color.