Campbell-scientific MD485 RS-485 Multidrop Interface Manual de usuario descargar pdf (Pagina 16)

MD485 RS-485 Multidrop Interface

active ports, while the remote MD485 has the active ports set to RS-485 and

CS I/O. With the MD485s configured as transparent devices, the only protocol

limitation is the fact that RS-485 is a half-duplex interface. If used with

traditional datalogger communication, PC software must take the half-duplex

nature of the link into account. For array-based dataloggers, this is

accomplished by PC400, LoggerNet, or PC208W.

RS-232

RS-485

CS I/O

To Wall Transformer

FIGURE 8. Long Distance RS-232 to CS I/O Conversion

Figure 9 shows how an MD485 could be used to send one-way data to a serial

printer via a P96 instruction. A null modem may be required in the RS-232

line for the printer. A transformer would be needed to power the MD485

nearest the printer, because the MD485 is not port-powered from the RS-232 or

RS-485 ports. In this configuration, the MD485 near the datalogger has CS I/O

and RS-485 as active ports. The CS I/O port should be configured to

Addressed Print Device which emulates a CSI SC99. RS-485 and RS-232 are

the active ports for the MD485 near the printer. Since printer data is one-way

only, the fact that the RS-485 interface is half-duplex is not an issue.

DIFF

GH L

AG H L AG H L AG E1 AG E2 G

DIFF

GH L

AG H L AG H L AG E3 AG G G

910

11 12

P1 G P2 G C8 C7 C6 C5 C4 C3 C2 C1 G 12V 12V

SDM

5V 5V G G

SW 12V

SW 12V CTRL

Logan, Utah

G 12V

POWER

CR10X WIRING PANEL

MADE IN USA

WIRING

PANEL NO.

EARTH

GROUND

CS I/O

RS-485

Null Modem Cable

To Wall Transformer

FIGURE 9. MD485 to Serial Printer

Figure 10 shows the MD485 used in a point-to-multipoint configuration. With

the MD485s in transparent mode, only a master-slave protocol is supported.

MODBUS is the only such protocol supported by CSI dataloggers and

commonly used in the SCADA industry.

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