# Council Regulation (EEC) No 3821/85 of 20 December 1985 on recording equipment in road transport, Appendix 6: EXTERNAL INTERFACES

Extent: E+W+S+N.I.

1.
HARDWARE
1.1.
Connector
INT_001 The downloading/calibration connector shall be a six pin connector, accessible on the front panel without the need to disconnect any part of the recording equipment, and shall comply with the following drawing (all dimensions in millimetres):
The following diagram shows a typical six pin mating plug:
1.2.
Contact allocation
INT_002 Contacts shall be allocated in accordance with the following table:
Pin
Description
Remark
1
Battery minus
Connected to the battery minus of the vehicle
2
Data communication
K-line (ISO 14 230-1)
3
RxD — Downloading
Data input to recording equipment
4
Input/output signal
Calibration
5
Permanent power output
The voltage range is specified to be that of the vehicle power minus 3V to allow for the voltage drop across the protective circuitry
Output 40 mA
6
TxD — Downloading
Data output from recording equipment
1.3.
Block diagram
INT_003 The block diagram shall comply with the following:
2.
DOWNLOADING INTERFACE
INT_004 The downloading interface shall comply to RS232 specifications.
INT_005 The downloading interface shall use one start bit, 8 data bits LSB first, one even parity bit and 1 stop bit.
Start bit one bit with logic level 0
Data bits transmitted with LSB first
Parity bit even parity
Stop bit one bit with logic level 1
When numerical data composed by more than one byte are transmitted, the most significant byte is transmitted first and the least significant byte last.
INT_006 Transmission baud rates shall be adjustable from 9 600 bps to 115 200 bps. Transmission shall be achieved at the highest possible transmission speed, the initial baud rate after a start of communication being set at 9 600 bps.
3.
CALIBRATION INTERFACE
INT_007 The data communication shall comply to ISO 14 230-1 Road vehicles — Diagnostic systems — Keyword protocol 2000 — Part 1: Physical layer, First edition: 1999.
INT_008 The input/output signal shall comply with the following electrical specification:
Parameter
Minimum
Typical
Maximum
Remark
U low (in)
1,0 V
I = 750 μA
U high (in)
4 V
I = 200 μA
Frequency
4 kHz
U low (in)
1,0 V
I = 1 mA
U high (out)
4 V
I = 1 mA
INT_009 The input/output signal shall comply with the following timing diagrams:
Sensor signal (out)
Test signal (in)
UTC clock signal (out)

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Source: https://www.legislation.gov.uk/eur/1985/3821/annex/2/appendix/6 (the official version)
Page: https://openlegislation.uk/eu-regulation-1985-3821/annex-2/appendix-6
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.