McQuay Micro Tech Open Protocol Driver Manual Page 3 of 35
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1. McQuay Micro Tech Open Protocol Description
This document describes the FieldServer driver used to tr ansfer data between a FieldServer and
MicroTech® controllers. Transfers are done using the controller's Data Terminal Comm unications
Protocol. In this document the protocol is referred to as the McQuay Micro Tech Open Protoco l.
The McQuay Micro Tech Open Protocol driver allo ws the FieldServer to transfer data to and from devices
over either RS-232 or RS- 485 using McQua y Micro Tec h Open Protocol. The FieldServer can emulate
either a Server or Client.
When emulating a Cl ient, the driver enables the FieldServer to request ‘Everything’ from the Mc Quay
device as well as a number of advanced options which allow specific fields to be read or written and
device scaling to be applied.
When emulating a Server, the driver pro vides an emulation of the byte memor y of a device and responds
to read and write requests.
The following important points and limitations should be noted before proceeding with this m anual.
1. Arising from a feature of the McQuay Micro Tech Open Protocol is the peculiarity, that when a multi-
byte value is written to a McQuay device, the write is done one byte at a time (one byte of data can
be transferred per poll/response mes sage pair) allowing for the poss ibility (at least for a short period)
that the multi byte value is only partially correct until all the messages have been completed.
2. The vendor equipment is lim ited to a maximum of 9600 baud. Given that each message packet can
only transfer one byte of data and that some data of interes t is multi-byte, users of this protocol
should expect low data transfer rates.
3. Port expansion is not supported f or this driver.
4. A document identified as Ed15050 MicroTech Network Operations contains important inform ation
regarding the connection requirements of 3rd part y equipment such as the FieldServer to a Microtech
network. The document also defines a number of limitations for such connec tions. The following
quotations from this document outline some of this information.