Campbell Hausfeld Serial I/O Interface SDM-SIO4 - Manual (Page 7)

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Section 1. Introduction
The SDM-SIO4 has four configurable serial RS232 ports which allow it to be connected
to intelligent serial sensors, display boards, printers or satellite links. It can also be used
in many other applications where the data is transferred in a serial fashion. This device
is designed to send data to and receive data from the sensors, and process it in parallel
with the datalogger’s own program sequence, thus making the complete datalogging
system faster and more efficient.
The SDM-SIO4 can handle the incoming and outgoing data in many different ways. It
can either send data in the same format as sent from the datalogger or it can be
programmed to send pre-stored data strings to the sensor. Combinations of data sent
from the datalogger and pre-stored strings can be sent, allowing complex formatted data
to be sent. For input, the SDM-SIO4 can transfer data in the same form as received from
a sensor to the datalogger, or it can be programmed to filter out critical data from a
sensor and only pass back the data the datalogger requires.
This manual assumes that you have a basic knowledge of the
terminology and theory of serial communications. For further
information please refer to one of the standard textbooks on
this subject.
1.1 What is the SDM-SIO4?
The SDM-SIO4 is a device that is connected to a datalogger through the
datalogger SDM port. The SDM port is specific to Campbell Scientific
dataloggers and acts as a high-speed data exchange mechanism. On some
dataloggers it is a dedicated port; on others it is implemented using control
ports C1, C2 and C3.
Figure 1, on the next page, is a Schematic Diagram giving an overview of
the functions of the SDM-SIO4. When used in conjunction with the
following sections of this manual, it may help you to understand how the
SDM-SIO4 operates.
The datalogger program controls the sequence and timing of data exchange
with the sensors. However, unlike most other Campbell Scientific interfaces
the SDM-SIO4 can be configured in two ways:
1. By inserting commands in the datalogger program
2. By connecting a computer running a terminal emulation program to
serial port 1 on the SDM-SIO4. Pressing a switch on the SDM-SIO4
temporarily switches this port to allow you to access a ‘command line’
(for entering command strings in much the same way as entering
commands at the DOS prompt on a PC).
The ‘command line’ option allows you to store complex output strings and
data filters in the SDM-SIO4. This set-up information is stored in battery-
backed, write-protected memory, which allows you to set up the SDM-SIO4
in the office and then move it to the site of installation in an unpowered
state.
NOTE