Introduction; Overview; Communication Port - Honeywell SPM Technical Handbook

A.1 Introduction
A.1.1 Overview
If you have purchased the Digital RS422 output option
(P/N 870931 or 870995 for Z-Purge units only), your
SPM instrument is equipped with a serial remote device
communication port. The data available from this
communication port is intended to help you monitor SPM
operation from another location. It will also allow you to
gather gas concentration data for any use or analysis.
This manual will supply you with the technical
information for the use and correct operation of the SPM
protocol, which will allow you to communicate with this
sophisticated modular instrument. The SPM protocol
was designed and developed by Honeywell Analytics,
and is considered proprietary to Honeywell Analytics.
The following pages will describe to you what protocol
is, what the pieces are and how it is used. It will also
offer suggestions on most effective use.
The SPM protocol has been designed to be flexible and
efficient. The protocol is a byte-wise protocol. That is,
it is communicating information transferring bytes of
data back and forth between the instrument and your
computer equipment. A group of bytes is referred to as
a "packet".
A.1.2 Communication Port
Access to the SPM protocol is through the Amphenol
(Bendix) connector that is located on the side of the SPM
(located inside of purged units). Your SPM instrument
communicates through this port. This port also allows
your equipment to monitor what the SPM instrument is
actually doing from a remote area. This port is designed
to be bi-directional, that is, it will both send and receive
data.
SPM Technical Handbook
SPM Single Point Monitor
The SPM instrument's communication port is indicated
by a label "RS-422 output". The signals that are present
on the connector conform to RS-422 specifications. The
pin-out designations may be found in Section .
Your SPM will communicate at baud rate of 9600 baud
(sometimes specified as 9.6k baud). This is a fixed
value, and cannot be changed or adjusted by the user.
The SPM uses 8 bits per character, with one (1) stop
bit and NO parity.
The SPM protocol has been designed to be flexible
and efficient. The protocol is a byte-wise protocol. It
communicates information by transferring bytes of
data back and forth between the instrument and your
computer equipment. A group of bytes is referred to as
a "packet".
The communication port in the SPM can only exchange
one piece of information at a time. The SPM will only
accept a packet after it has sent a packet. It will ignore
any packet that your equipment sends that is not in
response to an SPM packet.
The SPM protocol is also used by the available
compliment of remote devices for the SPM. For example,
the TGM (Toxic Gas Monitoring) System uses the SPM
remote device communication port. Additionally, the
SPM protocol has been designed to support multiple
devices from its port, if required.
The 9 pin connector, marked as "RS-422 OUTPUT" is
the connector you use. Often it is referred to as a port
or as the communication port. It is a DB-9F form. Table
A-1 lists the signals that are available at the Network
Interface connector.
A-2