Calculating overall cable length, Using modems, Dip switch configuration – Rockwell Automation 1400-SP PowerMonitor Software User Manual

Page 74

Appendix B
Communications Application Note

B–6

Figure B–3
RS–485 Intermediate Terminal Strip Connection

ОООООО

ОО

ОООООО

ОО

ОООООО

RS–485 Terminals

–

SHLD

RS-485 Device

RS–485 Cable:

22 gauge shielded

twisted pair

TERMINAL STRIP

To IBM PC or other
RS–485 devices

DISTANCE X

NOTE: When an intermediate terminal block is used to connect any device to the RS–485 bus, the length of the cable segments between the device and the terminal
block must be taken into account when calculating the overall length of cable (4,000 ft. max.). This length is equal to 2 times distance X in the diagram.

When determining the overall length of an RS–485 communication straight
line or loop connection, it is important to account for all cable segments.
For example, when RS–485 connections to the device are made via an
intermediate terminal block, the lengths of cable between the device and the
terminal block must be added to the total cable distance (see Figure B–3).

If communications over a telephone network is used with modems, each
modem will require configuration.

If the modems used are configured using hardware DIP switches or a similar
method, set the DIP switches to provide the functionality outlined in Chapter
3, Section 3.1.3.

For modems that are configured via their communications port, the
Powermonitor Software automatically executes a predefined procedure at the
time that the operator selects the MODEM (TOUCH TONE) or MODEM
(PULSE) option in the CONNECTION screen.

This procedure automatically transmits two sets of commands to the
modem(s) which will configure both a Hayes–compatible 2400 baud modem
and a Hayes–compatible 9600 baud modem.

Calculating Overall Cable
Length

Using Modems

DIP Switch Configuration

Configuration Via
Communications – Standard
Modem Setup