Tait T2000-A76 Operation Manual

T2000-A76 AVL Modem

Operation Manual

© Tait Electronics Limited

Corporate HQ: PO Box 1645, Christchurch,

New Zealand.

Tel: [phone]

Fax: [phone]

Web: www.taitworld.com/

March 2003

M2303-00-P00-805

Contents

Section Title Page

1 Overview 5
1 Operation 6
2 Compatibility 8
3 GPS Interfaces 9
4 Programming the A76 12
5 Operation Sequences 14
6 Commands to the Remote Radio 17
7 Responses from the Remote Radio 21
8 CCDI Reference 24

March 2003 M2303-00-P00-805 5

1 Overview

The T2000-A76 AVL Modem is fitted as an options PCB within a T201X mobile radio. The AVL enabled T201X
radio collects and stores AVL data from a GPS receiver in its internal memory, which can then be relayed to
central control equipment.

A typical AVL system comprises:

• a remote GPS receiver

• a remote AVL T201X radio with a T2000-A76 fitted internally

• a despatcher radio at the central control (CCDI capable T201X, Tait Orca or TRM )

• a central control personal computer (PC) running an AVL application (e.g. SmartTrac)

The AVL application instructs the despatcher radio to poll the remote radio for AVL position and velocity data
which, when returned, is stored by the AVL application. The remote radio can also be set to emergency mode
where it periodically sends unsolicited AVL data to the despatcher radio.

The despatcher radios uses the Tait CCDI (Computer Controlled Data Interface) over-air command protocol to
communicate with the remote radio. CCDI commands containing short data massages (SDMs) are sent to the
remote radio by the PC AVL application. Each SDM contains a command which tells the remote radio to one
of the following:

• send an AVL report

• send database information

• set the Group Delay Time

• control the AUX line output

• reset the radio

The despatcher radio is CCDI capable and connects to the PC by a serial line using standard RS232 signals.

The GPS receiver sends data to the A76 using the NMEA-0183 data transfer protocol. The A76 interprets the
RMC sentance from the GPS receiver.

Programming of the A76 is done using a special programming application from a PC via the serial port. Only
the Group Delay Time which enables group polling of radios can be programmed remotely.

Glossary

AVL Automatic Vehicle Location NMEA National Marine Electronics Association
GPS Global Positioning System RMC Recommended Minimum (specific GPS/transit data)
SDM Short Data Message UTC Universal Time Code

6 M2303-00-P00-805 March 2003

2 Operation

Features

The A76 modem in the T201X radio performs the following AVL functions:

• AVL data collection from the GPS receiver

• simple AVL polling by the despatcher radio

• group AVL polling by the despatcher radio

• emergency unsolicited AVL reports to the despatcher radio

• PTT generated AVL reports

• AVL data transfer to another radio using the CCDI over-air protocol

• A76 configuration database modifications using Tait proprietary NMEA style messages

• auxiliary output control using RS232 CTS line

• FFSK tone blanking when data received

• reads the version of A76 firmware over-air

• programs the Group Delay Time over-air so that group polling can be configured

• reads the programmed Group Delay Time setting over-air

• over-air reset of the remote radio with or without initiating database

AVL Data Collection

The A76 modem collects and stores NMEA RMC data at intervals set by the GPS receiver. When a AVL poll is
sent from the AVL application to the remote AVL radio or an emergency activation occurs, an AVL report with
the stored data is immediately sent to the despatcher radio and saved by the AVL application. Refer to the
section , NMEA-0183 RMC Sentence Format, for a description of the NMEA RCM format. All RMC fields are
initialised with ‘0’.

Radio Signalling

The signalling between the despatcher radio and the remote AVL radio uses the Tait CCDI V2.0 terminal and
over-air protocol. CCDI Short Data Messages (SDMs) are used to send commands to the remote AVL radio and
to pass information back to the central control computer.

Auxiliary Output

The auxiliary output from the A76 uses the RS232 CTS line on the serial port to switch external devices on or
off. It can be remotely controlled by the despatcher radio by sending a AUX ON or AUX OFF message. Refer to
the Auxiliary Output Control section. This feature can be enabled or disabled by the A76 configuration.

Emergency Mode

Emergency mode is activated by the RTS input on the A76 serial port. If asserted, the A76 enters Emergency
mode and sends unsolicited reports at preset intervals. Refer to the Emergency Mode Activation section.

The Emergency mode feature can be enabled or disabled by the A76 configuration.

March 2003 M2303-00-P00-805 7

PTT Activated AVL Reporting

The A76 can be configured to send an unsolicited AVL report each time the PTT is pressed or released. Refer
to the PTT Activated AVL Reporting section.

FFSK Tone Blanking

Tone Blanking is used for applications in which voice and data share the same channel. When valid data is
received, the FFSK Tone Blanking mutes the radio. If the A76 detect either preamble or synchronisation bytes
in the received FFSK data, the speaker is muted using the squelch line. Refer to the Programming the A76
section for database configuration information.

Error Handling

‘old’ If the NMEA RMC data from the GPS receiver has the status flag set to ‘V’ (invalid),

the AVL report is marked as ‘old’.

‘not operational’ If no AVL data is received from the GPS receiver for 20 seconds, an AVL report

marked ‘not operational’ is sent. The will occur if the GPS receiver is disconnected.

‘format error’ If a data error occurs, an AVL report is marked ‘format error’ is sent. This may be

due to mismatched baud rates, an incorrect checksum or corrupt NMEA data.

Refer to section 8, Responses from the Remote Radio, for the response message format details.

A76 Configuration

Programming using NMEA

The serial RS232 serial port on the A76 modem is configured to expect NMEA type format. This means that
the programming of the A76 database must be done using NMEA sentences rather than sending a standard
CCDI Program command as is used with both the T2000-A75 Modem and the Tat Orca/Tait Radio Modem.

For this purpose four new Tait proprietry NMEA messages have been created:

• PTPGM - for programming the database configuration

• PTWDB - response from the A76 ro a PTPGM message

• PTRDB - for reading the database configuration

• PTDAT - response from the A76 ro a PTRDB message

Refer to the Programming the A76 section for details of the PTPGM settings.

Remote programming of Group Delay Time

The Group Delay Time is the only database configuration item that can be programmed remotely.

This is done using the Program Database command with a SEND_SDM CCDI message. Refer tothe Commands

to the Remote Radio section for further details.

The Group Delay Time determines the time that a radio waits before responding to a AVL report Poll. This is so
that when a Group Poll is sent, all the radios in the group respond at different intervals rather then
simultaneously.

8 M2303-00-P00-805 March 2003

3 Compatibility

T201X Radio Firmware

When programming the T201X radio firmware for use with the CCDI, use version 3.01 or greater.

Retrofitting an A76 AVL modem into a T201X radio, radios require radio firmware version 2.22 or later. If your
radio uses an earlier firmware version, a new microprocessor can be purchased as a separate item. Contact
your nearest authorised Tait dealer.

Remote Radio PGM Settings

When the A76 AVL modem board is fitted, the T201X PGM program settings have the following constraints:

• ‘BCD Channel Selection’ should be enabled and polarity set to Normal so that the A76 can change the
radio channel.

• Economy mode reduces the radio’s power consumption when it is idle. When economy mode is active
and there has been no valid activity on a channel for the duration of the economy mode timer, the
radio begins economy cycling. This means that the beginning of a transmission may be lost if it is
received after a period of inactivity.
If ‘Economy mode’ is enabled in a T201X with a CCDI modem fitted, set the default Lead In Delay in
the A76 configuration to 200 ms or greater.
The Lead In Delay can be reprogrammed as low as 40 ms, but the Economy mode must be disabled.

Despatcher Radio PGM Settings

The despatcher radio may be a Tait Orca, a Tait Radio Modem or a T2000 with a A75 fitted. Regardless of
which radio is used, the modem must have Auto Acknowledge set to disabled.

GPS Receiver

The GPS receivers supported must use the National Marine Electronics Association (NMEA) 0183 version 2.01
(or compatible) RMC serial communication standard with suitable transmission rate and data format.

Tait Supports two different types of receivers.

The T2002-A00 GPS Receiver

The T2002-A00 GPS Receiver is a weatherproof receiver suitable for mounting outside a vehicle. It requires

13.8V which needs to be supplied on pin 6 of the RS232 socket at the rear of the T201x. This is generally
supplied from S14 pin 1 of the T2000 Logic PCB.

The T2002-A00 has an optional mounting bracket (T2002-A01).

The T2003-A00 GPS Receiver

The T2003-A00 GPS Receiver is suitable for internal mounting. It requires 5V which needs to be supplied on
pin 4 of the RS232 socket at the rear of the T201x. This is generally supplied from S14 pin 2 of the T2000
Logic PCB.

March 2003 M2303-00-P00-805 9

4 GPS Interfaces

RS232 Interface

The RS232 interface on the despatcher radio has the following parameters which are fixed in the radio
modem firmware.

For every byte sent, there are 10 bits sent including the start and stop bits:

• Number of data bits = 8

• Parity = none

• Number of start bits = 1 (set to ‘1’)

• Number of stop bit = 1 (set to ‘0’)

The RS232 D-Range socket at the rear of the T201X radio has the following configuration:

* not available in the standard T201X without a T2000-A76 PCB fitted.

Caution: Note that RS232 pin labelling can be misleading. A straight-trough cable is used to connect the

GPS receiver to the T201x radio..

Note: The start and stop bits are removed by the modem for the over-air transmission of data. The FFSK data
sent is pure binary 8 bit data only.

Connections Function Connections Function

1 Not used 6 T2002-A00 supply
2TXD7

RTS

*

3RXD8

CTS

*

4 T2003-A00 supply 9 Not used
5 GND