IDENT-I • IRI-KHD2-4.RX, IRI-KHA6-4.RX
Operating control interface units using the 3964R protocol
Subject to reasonable modifications due to technical advances.
Copyright Fuchs, Printed in Germany
Fuchs Group • Tel.: Germany (06 21) 7 76-0 • USA (330) 4 25 35 55 • Singapore 7 79 90 91 • Internet http://www.pepperl-fuchs.com
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Operating control interface units using the 3964R protocol
8.1
Notes on the 3964R protocol
The 3964R procedure was defined to allow the transfer of data via a serial point-to-
point connection in which the majority of data errors and time-outs are detected and
corrected by the protocol. The 3964R protocol is an asynchronous bit-serial transmis-
sion procedure. A character frame consists of one start bit, 8 data bits, one even parity
bit and one stop bit.
The transmission rate is set via DIP switches S1, S2, and S3.
Communication always starts with a command message either to transmit data
(SEND messages) or to fetch data (FETCH messages).
The control interface unit replies with a "Response" message, with or without data.
A SEND message comprises a message header and data. A FETCH message com-
prises a message header only.
The message header consists of 10 bytes of information about the data target in the
case of a SEND message, or information on the data source, in the case of a FETCH
message.
If the RK 512 Interpreter is used, the message header is structured as follows:
Start
bit
0
LSB
1
2
3
4
5
6
7
MSB
Even
parity
Stop
bit
Byte
Code
Description
Check
1
00h
Message
yes
2
00h
Identifier
yes
3
’E’
Message "input"
yes
4
x
Type of data
no
5
xx
Target address of data
(high)
no
6
xx
Target address of data
(low)
no
7
yy
Volume of data (high)
no
8
yy
Volume of data (low)
no
9
FFh
Coordination marker
no
10
FFh
Coordination marker
no
