FS-8700-79 – GCM ASCII Serial Driver

FieldServer Driver


GCM ASCII Serial Driver




The Barber Coleman Network 8000 system consists of a number of different device types which connect using a number of communication connection technologies.

This driver is designed to connect to a GCM device and to read and write data from the GCM and a limited set of remotely connected devices.

The driver is an active client driver. This means that it initiates read / write polls with the GCM (Barber Coleman  Network 8000) GCM device, which is expected to provide responses.  Server functionality is not provided by in this driver.

The following brief notes provide an overview of the drivers functionality

  • The driver can read (and write) most ‘block’ data in the GCM.  Since GCM blocks are programmed to provide current data from emote device connected using the ASD and other busses, this means that the driver can read and write data to remote devices connected on the ASD bus. These devices include the MicroZone and MicroFlow controllers.
  • The driver can read (and overwrite or force) most data points in a remotely connected LCM device. When reading from the LCM the driver can store all current status variable values or specific variables, depending on the configuration.
  • The driver has no advanced knowledge of the GCM or other Network devices and their data blocks. Therefore it cannot validate block or variables names specified in the configuration file. In addition, this means that the driver handles each variable/block in a generic way and without regard for the particular variables that constitute the tables.


Formal Driver Type


Client Only


Connection Information

Connection type: EIA232 or EIA485 (Two wire, Half-Duplex)

Baud Rates: 9600;  (Driver is capable of others, Vendor equipment isn’t.)

Data Bits: 8  (Vendor equipment limitation)

Stop Bits: 1 (Vendor equipment limitation)

Parity: None  (Vendor equipment limitation)

Hardware interface: None

Multidrop Capability No


Devices tested:

Device Tested
GCM-84121-S-0-1LCM-88210-1 Factory


Connection configurations


Connection Notes

Only one GCM device can be connected to each EIA232 or EIA485 (with converter) port at a time. This limitation arises from the fact that the message format is node-less; there is insufficient information in one message to differentiate messages from one GCM device to other.


Communications functions

Supported functions at a glance:


Read Block

Read Variable

Override (Write) Variable (Tested with LCM)



The  GCM ASC Serial Driver allows variables to be read from Gcm reports for ZONE2 block types and Current

status for LCMs


For Gcm Zone2 type blocks (Typically these blocks contain data from connected Microzone, MicorFLow and other ASD devices)


Driver can read all

  • DI,AI (EMS variables)
  • UI (A & D analog and digital)
  • Simple DO (Digital outputs)
  • Simple AO (Analog Outputs)
  • DV Digital values for Windows and Analog values for windows.


For LCM Current status

This driver can read variables from current status for LCM by referring its name but variable can be of either type

  • AO (analog Output),
  • AI(Analog Input) ,
  • DI (digital input)
  • DO (digital output) or
  • Loop


The driver can store data from other types of points too provided that the value and units can be parsed in a format that is similar to the AI/AO/DI/Do etc.


When a block or variable is read the following information can be stored in the FS’s Data Arrays. BY default the driver stores only the variable values but by extending the configuration the additional data can be stored.

  • variable name,
  • variable value,
  • variable type,
  • variable units

Override (Write)

The  GCM ASC Serial Driver allows variables to be override blocks’ parameters at GCM and  LCMs

The driver can override variables of any type without restriction. However, it may be the case that the N8000 system prevents writes to certain types of variables. The driver has been tested with AO and DO overrides with LCM.

Data Types Supported

The driver has no advance knowledge of the number, names , length and contents of any of the data blocks o be found in the N8000 networked devices. (These parameters are dependent on the type of devices). Therefore the driver handles all table variable values as one of the following types;

a) Numeric values

b) Discrete state’s converted to a numeric value.

c) Character Strings.

The driver chooses the data type automatically based on the response from the GCM device.


Limitations and Exclusions

The driver can Only read reports for block data of type ZONE2 and Current Status for LCM (model no.LCM-88210-1 ) and it can read only variable name, value, units and type only. This driver is tested override (write) block’s variable for specified LCM.

The driver cannot be configured to act as server.

The driver performance is slow. In situations where the driver is configured to read data from multiple remote devices or multiple device types expect response times that may range up to 10 seconds.  For example: If the driver has been configured to read data from more than one LCM connected to the GCM then performance will be slow because the driver needs to log into each LCM, navigate the menus, log out and log into the next LCM.

During testing variations in GCM, LCM and other device firmware were noted. Of the three GCM units used for testing, all three produced slight variations in the message stream. It is possible that other versions of firmware may produce other variations which may cause problems for the driver.


Revision History

Date DocumentRevision Resp Comment
9Sep03 0 SSS Draft, for internal and customer review only.
15Sep03 1 SSS Removed some “todo”
03Oct03 2 PMC Updated



If you liked this post;
  • Please consider subscribing to our RSS feed