User guide

PlantLinc PLR5000 User’s Guide

P/N 161-09888-001 DATA-LINC Group

Main Menu Option (1): Set Baud Rate

When option (1) is selected, you will be able to change the radio modem’s RS232 baud rate. This is the

communication rate between the radio modem and the instrument to which it is connected. It is important to

note that this is independent of the baud rate for the other radio modem(s) in the communication loop. For

example, PLR5000s may be used in an application to send data from remote process instrumentation to an

engineer’s computer. In this application, the baud rate for the radio modem on the instrumentation might be

set to 9600, and the radio modem on the computer might be set to 19,200 or 38,400.

In general, it is desirable to set the baud rate to the highest level supported by the device to which it is

connected. However, please note that this may actually result in slower data communications if the UART

chipset of the connected device does not support higher data rates.

ModBus RTU and various data word sizes and parity configurations

The additional features are support for ModBus RTU and support various data word lengths and parity. These

features are available under selection options (A) and (B).

There are six data word length and parity configurations available. In the Set Baud Rate menu select (A) and

type in the number corresponding to the configuration below. The default setting is 0 (8,N,1) and is the most

commonly used serial communications protocol.

Table 2: Available data word length and parity selections

Menu Setting Data Bits Parity Stop Bits

0 8 None 1

1 7 Even 1

2 7 Odd 1

3 8 None 2

4 8 Even 1

5 8 Odd 1

ModBus RTU

Support for ModBus RTU protocol is available. The default for the ModBus RTU setting is (0) not enabled.

To enable the ModBus RTU mode:

1. In the “Set Baud Rate” menu enter (B) and then select (1)

2. In the “Set Multi Point Parameters” menu, set Master Packet Repeat to (3).

Note: When using the PLR5000 radios in ModBus RTU mode the Master Packet Repeat must be set to (3)

regardless of whether the modems are being used in point-to-point or multipoint mode. If a setting that

is higher than (3) is required, it can be done, but the throughput speed will be decreased. (A higher

Master Packet Repeat setting may need to be used when the radios are in a high noise environment or at

long ranges).