Emerson S-series Serial Interface Product Description

Product Description

The Serial Interface consists of a serial card and a terminal

block. The card contains two serial communications

ports that support RS232 and RS422/485 half duplex, or

RS422/485 full duplex signals. These ports are individually

configurable and support data rates from 300 Baud up to

115 KBaud.

The S-series card plugs into an 8-wide I/O carriers in any of

the possible 64 slots and communicates with the S-series

controllers. LEDs, located on the front of the card, show the

power, error, and port status of the interface at a glance.

The standard Modbus protocol includes the Serial Interface,

the Modbus RTU, and ASCII communications protocol

as defined in the Modicon Modbus Protocol Reference

Manual dated March 1992 (PI-MBUS-300 REV D). Each Serial

Interface port may be configured as either a master or

slave device.

The serial card supports the following features using the

Modbus protocol:

• Reading input data from Modbus coils, input status,

holding registers and normal input registers.

• Writing output data to coils and holding registers.

• Output data can be written in single coil, register mode,

or complete data set mode. This output mode is a

configurable parameter.

• Input data can be read in as a complete data set,

providing the best performance.

The serial card supports the input and/or output of

16 different data sets per serial port, for a total of 32 data sets

per Serial Interface.

Serial dataset registers can be referenced directly in control

modules as analog or discrete I/O providing fast easy data

exchange with the serial device. Direct module-to-Dataset/

register references are recommended for control signals.

Alternatively, users can read multiple registers form a

Dataset into a single “marshalling” module at the cost of

a single DST. Marshalling modules provide a cost effective

way to integrate serial data from analyzers and other data

sources. Serial dataset registers can also be passed as

SCADA values directly to Workstations and Continuous

Historians without consuming DST’s.

Both Modbus RTU and Modbus ASCII communications

modes are supported by standard Modbus protocol.