Eurotherm 4181/4250 Manuale del proprietario

ε

EUROTHERM

4181/4250

180/250 mm Chart Recorders

Serial

Communications

Manual

COMMUNICATIONS MANUAL

HA246958

Issue 14 Mar 02

Page 1

Communications Manual

List of contents

Section Page

Continued

1 INTRODUCTION ......................................................... 3

2 INSTALLATION ........................................................... 4

2.1 INSTALLATION OF ORIGINAL VERSION

(OLDER 250mm RECORDERS ONLY) ......... 4

2.1.1 Mode selection......................................................................5

2.2 ISOLATED VERSION INSTALLATION ..................................... 6

2.2.1 Installation for 250 mm recorders .............................................6

MULTIPOINT RECORDERS .................................................6

CONTINUOUS TRACE RECORDERS ..................................6

2.2.2 Installation for 180 mm recorders ............................................7

2.2.3 Mode selection......................................................................9

2.3 COMMUNICATIONS WIRING ............................................ 9

2.3.1 Original version ....................................................................9

2.3.2 Isolated version .....................................................................9

2.3.3 Termination and biasing (not RS232) .......................................11

HOST COMPUTER ...........................................................11

2.3.4 On-board links ......................................................................13

2.4 HARDWARE CONFIGURATION........................................... 14

2.4.1 Communications parameters ...................................................14

2.4.2 Handshake ...........................................................................14

HARDWARE HANDSHAKE ...............................................14

SOFTWARE HANDSHAKE ................................................14

3 MODEL 4001 COMMUNICATIONS ....................................... 15

3.1 COMMUNICATIONS PROTOCOLS............................. 15

3.1.1 ANS I.................................................................................15

POLLING.........................................................................15

SELECTION .....................................................................16

3.1.2 ASCII ..................................................................................16

3.2 PARAMETER ADDRESSING ................................................. 17

3.3 DATA FORMATS................................................................. 17

3.3.1 Hexadecimal (Hex) ................................................................17

3.3.2 Decimal (Floating point) .........................................................17

3.3.3 Character .............................................................................17

All rights are strictly reserved. No part of this document may be reproduced, modified, or transmitted in

any form by any means, nor may it be stored in a retrieval system other than for the purpose to act as an

aid in operating the equipment to which the document relates, without the prior written permission of

Eurotherm limited.

Eurotherm Limited pursues a policy of continuous development and product improvement. The specifi-

cations in this document may therefore be changed without notice. The information in this document is

given in good faith, but is intended for guidance only. Eurotherm Limited will accept no responsibility

for any losses arising from errors in this document.

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COMMUNICATIONS MANUAL

List of contents (Cont.)

Section Page

3.4 MNEMONICS ................................................................... 18

3.4.1 Channel mnemonics...............................................................19

INPUT CHANNELS...........................................................20

OUTPUT CHANNELS........................................................22

DERIVED CHANNELS .......................................................24

3.4.2 Alarm mnemonics ..................................................................25

ALARM BUFFER VALIDATION CHECKS. ..............................25

3.4.3 Instrument mnemonics ............................................................27

3.5 COMMAND MNEMONICS ................................................ 31

3.5.1 Alarm acknowledge (AA) .......................................................31

3.5.2 Printer on (CG)......................................................................31

3.5.3 Chart halt (CH)......................................................................31

3.5.4 Printer off (CO)......................................................................31

3.5.5 Chart Wind (CW) .................................................................31

3.5.6 Data Dump (DD)....................................................................31

3.5.7 Disable program mode (DP)....................................................31

3.5.8 Enter alarm data (EA).............................................................31

3.5.9 Enter channel data (EC)..........................................................31

3.5.10 Enable program mode (EP) ...................................................31

3.5.11 Get indicated alarm data (GA)..............................................32

NO MATHS PACK FITTED .................................................32

MATHS PACK FITTED........................................................32

3.5.12 Get free alarm (GF) .............................................................32

3.5.13 Chart rewind (CR) ...............................................................32

3.6 PARAMETER SCROLLING .................................................... 33

3.6.1 Block parameters...................................................................33

3.6.2 Scroll parameters ..................................................................33

ALARM PARAMETERS .......................................................33

INSTRUMENT PARAMETERS..............................................33

3.7 CHARACTER SET ............................................................... 34

3.8 APPLICATION NOTES ........................................................ 40

3.8.1 Message timing.....................................................................40

3.8.2 Command mnemonics............................................................40

3.8.3 Channel selection ..................................................................40

3.8.4 Alarm selection / polling ........................................................40

SELECTION .....................................................................40

3.8.5 Printed text ...........................................................................40

3.8.6 Special characters .................................................................41

ASCII MODE ...................................................................41

ANSI MODE ...................................................................41

3.8.7 Multi-parameter data packets ..................................................41

3.8.8 Digital input channels.............................................................41

3.8.9 Floating point overflow...........................................................41

4 GOULD MODICON MODBUS PROTOCOL..................... 42

4.1 CHANNEL ADDRESSING.................................................... 42

4.2 READING ANALOGUE VALUES........................................... 42

4.2.1 16-bit format .........................................................................42

4.2.2 32-bit format .........................................................................43

EXAMPLE 1 READ CHANNEL 05 .......................................43

TOTALISER VALUES...........................................................43

4.3 FUNCTION CODES ........................................................... 44

5 XMODEM TRANSFER .................................................. 46

6 LIST OF EFFECTIVE PAGES ........................................... 47

INDEX ........................................................................... 48

COMMUNICATIONS MANUAL

HA246958

Issue 14 Mar 02

Page 3

COMMUNICATIONS

1 INTRODUCTION

This manual is intended as an aid to those involved in the installation and operation of a serial communications link

between one or more chart recorders (or I/O racks) and a host computer.

Section 2 describes the physical installation of a communications option and its hardware set-up and wiring.

Section 3 describes host communications protocol emulation of the 4001 communications protocol allowing customers

with model 4001 recorders to transfer their communications programs to more modern recorders without difficulty.

Section 4 deals with the Gould Modicon Modbus RTU protocol.

Section 5 gives a procedure for XMODEM file transfers, for saving and restoring recorder configurations.

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COMMUNICATIONS MANUAL

2 INSTALLATION

The communications option is in two versions. The original version has a 25-way D-type connector, whilst the newer

(isolated) version has two 9-way D-type connectors - one plug; one socket. Before installation is carried out, it is rec-

ommended that the links on the circuit board be checked against figure 2.3.4 to ensure correct positioning.

2.1 INSTALLATION OF ORIGINAL VERSION (OLDER 250MM RECORDERS ONLY)

This section describes the installation of the communication option in the box located at the rear of the recorder. For

those recorders already fitted with the option, this section may be ignored.

CAUTION

THE CIRCUIT BOARD INCLUDED AS A PART OF THE KIT CONTAINS COMPONENTS WHICH

ARE SENSITIVE TO STATIC ELECTRICAL DISCHARGE. ALL RELEVANT PERSONNEL SHOULD

BE AWARE OF STATIC HANDLING PROCEDURES. IF IN DOUBT, CONSULT THE RELEVANT

SECTIONS OF EITHER THE INSTALLATION AND OPERATION MANUAL OR OF THE TECHNI-

CAL MANUAL.

The communications option kit consists of a circuit board, two screws and two labels. The installation procedure is as

follows. Reference should be made to figures 2.1a and 2.1b as required.

a. Remove the battery cover, retaining it and its securing screws for later re-assembly.

b. Remove the communications box by removing the two securing nuts. Retain these nuts and their associated shake-

proof washers for use in re-assembly.

c. Knock out the three slots in the box.

d. Fit the labels supplied

e. After taking precautions against static discharge, screw the circuit board to the box.

f. Plug the assembled box into the connector at the rear of the recorder.

g. Fix the box to the recorder using the nuts and shake-proof washers previously removed.

h. Refit the battery cover.

i. Select RS232 or RS422/485 (section 2.1.1 below), then carry out an autoconfigure as described in the installation

and operation manual supplied with the recorder.

Figure 2.1a Battery cover and communications box location

COMMUNICATIONS MANUAL

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Issue 14 Mar 02

Page 5

2.1 INSTALLATION OF ORIGINAL VERSION (Cont.)

Figure 2.1b Communications option assembly

2.1.1 Mode selection

The communications can be set to RS232 or RS422/RS485 by sliding all the

elements of the DIL switch to the right (RS232) or to the left (RS422/485).

In RS232 mode, the LEDs show their stated functions. The LEDs are off when

the relevant lines are idle, and are illuminated when they are active.

In RS422/485 mode, only the transmit (Tx) and receive (Rx) LEDs are opera-

tive. These LEDs are off when the lines are at idle, and are illuminated when

they are active.

The pin allocations for RS422/485 and RS232 are shown in section 2.3.1 below.

Note: Four wire (TXA/B, RXA/B) RS485 is supported; two wire RS485 is

not supported.

Figure 2.1.1

Communications set-up switches

Knock out

holes

Fit labels

1

2

3

Fit board to box

4

Plug box into

recorder

25-Way D-type

socket

Set all elements left for

RS42/RS485, or right for RS232C

Tx

Rx

RTS

CTS

DTR

DSR

Comms status

LEDs

BC

D

E

FA

2

3

4

5

61

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COMMUNICATIONS MANUAL

2.2 ISOLATED VERSION INSTALLATION

2.2.1 Installation for 250 mm recorders

MULTIPOINT RECORDERS

With the recorder isolated from hazardous voltages, remove the battery cover and dummy comms box (if fitted) as

described in section 2.1 instructions 'a' and 'b'. Fit the comms module supplied with the kit, ensuring that the connector

is correctly mated before tightening the fixings and replacing the battery cover.

Re-apply power to the recorder, switch on and carry out an Autoconfigure, as described in the installation and operation

manual supplied with the recorder.

CONTINUOUS TRACE RECORDERS

With the recorder isolated from hazardous voltages, take

the ribbon cable supplied with the kit, and plug it into the

header on the comms module circuit board.

Pass the ribbon cable through the slot in the rear of the

recorder, then secure the comms module to the recorder

using two nuts.

Open the recorder door and release the writing system by

undoing the two captive screws (fig 2.2.1a)

Pull the writing system forwards until access can be gained

to the control board mounted at the rear.

Plug the free end of the ribbon cable into CON 3 on the

control board (figure 2.2.1b).

Return the writing system to the case and

secure it, using the two captive screws.

Set the comms module to RS232 or RS422/

485 as described in section 2.2.3.

Re-apply power to the recorder, switch on

and carry out an Autoconfigure, as de-

scribed in the installation and operation

manual supplied with the recorder.

Figure 2.2.1a Writing system securing screws

Figure 2.2.1b Communications connector location

CON3

(Communications)

COMMUNICATIONS MANUAL

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Issue 11 Dec 97

Page 7

A

Figure 2.2.2a

Writing system securing screws

Figure 2.2.2b Writing system removal

and PSU securing screw locations

Figure 2.2.2c

PSU release (rear view)

Figure 2.2.2e PSU removal

Figure 2.2.2d Battery pack disconnection

B

C

D

2.2.2 Installation for 180 mm recorders

CAUTION

THIS UPGRADE INVOLVES THE HANDLING OF COMPONENTS WHICH ARE SENSITIVE TO

STATIC ELECTRICAL DISCHARGE. ALL RELEVANT PERSONNEL MUST BE AWARE OF STATIC

HANDLING PROCEDURES. IF IN DOUBT, REFERENCE SHOULD BE MADE TO THE INSTAL-

LATION AND OPERATION MANUAL OR THE TECHNICAL MANUAL.

1. Isolate the recorder from all high voltage sources (both supply

and signal)

2. Open the recorder door (by lifting the bottom of the catch, and

then turning it clockwise) For convenience, remove the chart and

print cartridge.

3. With the cassette open, Release the writing system by undoing

the captive screws (‘A’ in figure 2.2.2a)

4. Pull the writing system forwards until it reaches its stops.

5. Lift the writing system out of the case, releasing the various con-

nectors as they become accessible (figure 2.2.2b).

6. Release the Power supply unit from the front, using screws ‘B’ in

figure 2.2.2b, then from the back, by removing the safety earth

(nut ‘C’ in figure 2.2.2c) and securing screw ‘D’.

7. Disconnect the battery pack as shown in figure 2.2.2d

8. Rotate and lift out the power supply as shown in figure 2.2.2e,

carefully avoiding damage to the battery pack connector.

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COMMUNICATIONS MANUAL

2.2.2 INSTALLATION FOR 180mm RECORDERS (Cont.)

9. Fit the plastic cable clip as shown in figure 2.2.2f.

10. At the rear of the recorder, remove the blanking plate, and fit the communications module (figure 2.2.2g).

11. Feed the communications module ribbon cable across the inside back of the recorder, secure it with the clip, then

fold the cable back on itself and make a right angle turn upwards (figure 2.2.2f).

12. Re-fit the power supply unit, and ensuring that the battery pack connector is passed through its aperture, secure it

at the front and at the back, using the four screws and safety earth nut previously removed.

ENSURE THAT

THE SAFETY EARTH IS SECURELY TERMINATED.

13. Return the writing system to the case, ensuring all the connectors are re-made.

14. Re-apply power to the recorder, and carryout an Autoconfigure as described in the Installation and Operation

manual suppled with the recorder.

To comms

module

To control

board

Cable clip

65 mm

70 mm

View on inside of case;

bottom left-hand corner

Figure 2.2.2f Cable clip location

Figure 2.2.2h Routing cables and returning the PSU Figure 2.2.2i Communications connector location

Figure 2.2.2g Comms module fitting

COMMUNICATIONS MANUAL

HA246958

Issue 11 Dec 97

Page 9

2.2.3 Mode selection

Once physical installation is complete, the communications mode should be set up as RS232 (Single drop) or RS422/

RS485 (Multiple drop) before electrical connections are made.

The selection of communications mode is made by setting ALL of the switches located between the two 9-way D-types

up for RS232 or down for RS422/485*, as shown on the communications module label.

* The module is mounted ‘sideways’ on Graphics Display Units. The switches should be set left for RS232 or right for

RS422/485.

Figure 2.2.3 Set-up switch locations (isolated version)

2.3 COMMUNICATIONS WIRING

2.3.1 Original version

The serial link is implemented using a 25-way D-type (fixed socket) connector. Table 2.3 gives pin-out information for

RS232C and for RS422/485. Recorder Tx should be connected to the host Rx and vice-versa.

2.3.2 Isolated version

Tx should be connected to Rx at the host and vice-versa.

The serial link is implemented using two 9-way D-type connectors. For non-graphics instruments set to RS422/485,

the two connectors are wired in parallel for easy ‘daisy-chaining’ in multi-drop applications. For non-graphics instru-

ments set to RS232, and for all data acquisition racks, only the ‘male’ connector (plug) is to be used.

See the graphics unit manual for graphics recorders/display units details.

Note: The signal ground MUST be earthed at one point (only) in the link.

9-way socket

9-way plug

Set all switches up for RS232.

Set all switches down for RS422/485.

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COMMUNICATIONS MANUAL

2.3 COMMUNICATIONS WIRING (Cont.)

Table 2.3 Communications module pinouts

1

2

3

4

5

6

7

8

9

5V

1k0

RX

TX

DTR

Signal ground

DSR

RTS

CTS

Not connected

Function

RS232 Pin out

(Switches up)

(Fixed plug only)

1

2

3

4

5

6

7

8

9

TXA

TXB

Not connected

Signal ground

Not connected

RXB

RXA

Not connected

Function

RS422/485 Pin out

(Switches down)

(Plug or socket)

Comms pinouts for current recorders and I/O (data acquisition) racks.

(I/O racks may use only the fixed male connector (plug) for the serial link)

5V

1k0

Isolated Comms

(2 x 9-way D-types)

RS232 Terminations

Rx5v* Tx DTR 0V DSR RTS CTS

RS232 available with upper

connector only (all switches left)

RS422/485 Terminations

TxA5v* TxB NC 0V NC RxB RxA

Lower connector always RS422/485.

Upper connector selectable RS232

(all switches left) or RS424/485

(all switches right)

Comms pinouts for Graphics Display Units

1

2

3

4

5

6

7

19

20

5V

1k0

RX

TX

DTR

Signal ground

DSR

RTS

CTS

Function

RS232 Pin out

(Switches right)

TXA

TXB

Signal ground

Not connected

RXB

RXA

Not connected

Function

RS422/485 Pin out

(Switches left)

Comms pinouts for previous recorder versions

5V

1k0

Non-Isolated Comms

(25-way D-type)

Protective ground

1

2

3

4

5

6

7

19

20

Protective ground

COMMUNICATIONS MANUAL

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Issue 14 Mar 02

Page 11

2.3.3 Termination and biasing (not RS232)

If the communications line is left open-ended, the end of the cable acts as a reflector, returning what can appear to be

‘true’ data signals back down the line. A receiver cannot distinguish between ‘true’ and reflected data, with the result

that the ‘true’ data is corrupted.

In order to avoid this, a termination resistor is fitted across the line at the final instrument. If the value of this resistor

is equal to the characteristic impedance of the cable (120 Ohms in this case), then the line appears to be of infinite

length and no reflections occur. Such a value however, does not give the best signal-to-noise ratio, so a compromise

value (220 Ohms) is chosen to give the optimum performance in reducing unwanted reflections and in improving the

signal-to-noise ratio.

The recorder communications port is terminated as shown in figure 2.3.3a, below. In a single point-to-point applica-

tion, it may be necessary to terminate the instrument with a 220Ω resistor. In multi-drop systems, only the final unit

should be terminated in this way, otherwise the transmitted signal levels may be reduced to an unacceptable level.

Figure 2.3.3a System termination and biasing

HOST COMPUTER

When not communicating, the instrument outputs go to a high-impedance state to allow multi-drop connection. This

will cause a problem if the host computer is not fitted with biasing resistors to pull these essentially open circuit lines to

their idle states as defined for the RS422/RS485 standards. To overcome such problems, external biasing resistors can

be fitted as shown in figure 2.3.3b (a) below.

With long cable runs it may also be necessary to terminate the transmission line. Figure 2.3.3b (b) shows how this

may be done using external biasing resistors. Such a circuit is for use where the host receiver does not have its own

internal biasing arrangements. Where the host does have its own internal biasing, the fitting of a 220Ω resistor across

the receive inputs (figure 2.3.3b (c)) will terminate the line correctly.

RxB

Recorder A

Recorder B (Final recorder)

Transmit lines from host

TxB

TxA

RxB

RxA

220Ω

5 Volts

Receiver

device

0 Volts

100kΩ

0 Volts

5 Volts

100kΩ

Receiver

device

RxA

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COMMUNICATIONS MANUAL

2.3.3 TERMINATION AND BIASSING (Cont.)

Figure 2.3.3b Host computer termination and biasing

4k7

min.

0 Volts

TxB

TxA

Transmit lines from

recorder*

220R

Host

receiver

device

5 Volts

4k7

min.

c. Host with internal bias resistors and external termination.

5 Volts

4k7

TxB

TxA

Transmit lines from

recorder*

Host

receiver

device

0 Volts

4k7

a. Host with external bias resistors b. Host with external bias resistors providing

termination.

5 Volts

470R

0 Volts

TxB

TxA

Transmit lines from

recorder*

Host

receiver

device

470R

* For 'recorder' read 'Graphics unit',

'Data acquisition unit' etc. as appropriate

COMMUNICATIONS MANUAL

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Issue 14 Mar 02

Page 13

2.3.4 On-board links

When retro-fitting or replacing a communications board, a number of links need to be correctly set. The positions of

these links depends on the model as shown in the sketches below. The sketches show an issue 2 board. Issue 1 boards

are similar, but do not have links at 'A'. This is important only for I/O rack users.

The communications link is set to RS232 by setting all the toggle switches up (as shown in the figures) or to RS422/

485 by setting all the switches down.

Figure 2.3.4 Communications board link positions

AA

180/250mm continuous trace recorder (U100)

180mm multipoint recorder (U100)

250mm Multipoint recorder (U200)

180mm graphics recorder (U100)

250mm graphics recorder (U200)

A

Graphics display unit (U200)

A

I/O (Data acquisition) rack (U200)

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COMMUNICATIONS MANUAL

2.4 HARDWARE CONFIGURATION

Figure 2.4 Communications configuration

2.4.1 Communications parameters

Protocol 4001 ANSI* Uses ASCII codes, including control codes (e.g. STX)

4001 ASCII* Uses ASCII codes, but control codes are replaced by printing characters

(See section 3.1.2 below).

MODBUS RTU protocol. Fixed data bits = 8; No handshake.

Baud Rate 110 to 19,200 Scrollable 19,200, 9,600, 4,800, 2,400 1,200, 600, 300, 110

Parity Odd, even, none Allows parity to be set.

Data Bits 7, 8 Eight bits required for ‘special’ characters Hex 80 to E2 in table 3.7.

Stop bits 1, 2 Allows the number of stop bits to be set.

H/W Handshake On/Off Enables / Disables handshake.

Group Address 0 to 7 Group address (G) used as a part of the 4001 channel address.

Address 1 to 247 Gould Modicon address

* 4001 ASCII and 4001 ANSI protocols may not be applicable to all recorder models.

2.4.2 Handshake

Handshake is not applicable to MODBUS protocol.

HARDWARE HANDSHAKE

Hardware handshake operates with three signals CTS, RTS and DTR. DSR is ignored by the recorder.

When hardware handshake is ‘ON’, DTR and RTS outputs are set to their ‘ON’ condition (voltage +’ve) when the in-

strument is capable of communication. These signals will therefore be off during power up / initialisation etc. The

CTS input high to the instrument enables its transmitter.

When hardware handshake is set ‘OFF’ DTR and RTS are set to their OFF states (voltage -’ve). The CTS input is ig-

nored.

SOFTWARE HANDSHAKE

XON/XOFF handshaking is implemented in ASCII mode only (section 3.1.2). On receipt of XOFF (ASCII hex 13)

the recorder will stop transmitting at the end of the current character, and will not re-start transmission until it receives

XON (ASCII hex 11). All bytes received between XOFF and XON are ignored. Multiple XONs are ignored. The

instrument does not generate XON or XOFF.

Configuration : Select a category

MEMORY COMMS TRANSFER DIAGS MORE>

Protocol 4001 ANSI Baud Rate BBBBB

Parity Even Seven data bits

Top level

configuration menu

One stop bits Hardware handshake off

Group address 0

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3 MODEL 4001 COMMUNICATIONS

Note: 4001 communications protocols may not be available on all Models.

3.1 COMMUNICATIONS PROTOCOLS

3.1.1 ANSI

This is an implementation of the ANSI standard ANSI - X3.28 - 2.5 - A4 and specifies two modes: POLLING (for

reading values from an instrument), and SELECTING (for writing values to an instrument).

POLLING

The sequence of bytes sent to the instrument in order to read a value is:

Where:

G is the Group Address set up in the communications configuration.

U is a ‘Logical Unit’ number, associated with up to eight channel addresses.

CA is a channel address within the logical unit.

C1C2 is the two character mnemonic which defines the parameter to be read.

See table 3.2 for U and CA allocations, and tables 3.4.1, 3.4.2 and 3.4.3 for a mnemonic / parameter cross reference.

In response to such a polling message, the instrument will reply with one of the following:

POLL COMPLETE MESSAGE

<STX>[CA][C1][C2][D1][D2.......DN]<ETX>[BCC]

Where D1 to DN is the N byte value of the polled parameter. The number of bytes required is a function of the particu-

lar parameter polled. BCC is a block check control character which is the result of exclusive ORing bytes [CA] to

<ETX> inclusive. After a POLL COMPLETE message, the host can respond with <NAK> (which causes re-trans-

mission of the parameter previously polled), <ACK> (which polls the next parameter in the poll list (see section 3.6)),

or with a complete new polling message.

POLL INCOMPLETE MESSAGE

This indicates that there was an error in the polling message. The host must send a complete new polling message in

order to access the parameter (i.e. sending <ACK> or <NAK> does not have any effect).

NO RESPONSE

The polling message was not recognised.

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COMMUNICATIONS MANUAL

3.1 COMMUNICATIONS PROTOCOL (Cont.)

SELECTION

The sequence of bytes sent to the instrument in order to write a value to a parameter is:

Where:

G is the Group Address set up in the communications configuration.

U is a ‘Logical Unit’ number, associated with up to eight channel addresses.

CA is a channel address within the logical unit.

C1C2 is the two character mnemonic which defines the parameter to be read.

D1 to DN is the N-byte value to be written to the parameter.

BCC is a block check character calculated by exclusive ORing bytes CA to ETX inclusive.

See table 3.2 for U and CA allocations for current recorders and tables 3.4.1, 3.4.2 and 3.4.3 for a mnemonic / param-

eter cross reference.

In response to such a selection message, the instrument will reply with one of the following:

SELECTION COMPLETE MESSAGE

The instrument responds with a single <ACK>. The host may now re-enter the selection procedure after <STX> and

write a new [CA] to <BCC> message, providing that the new parameter is in the same logical unit as the last one (i.e.

[G] and [U] are the same). Alternatively, the host can send a complete new selection message.

SELECTION INCOMPLETE MESSAGE

The instrument responds with a single <NAK>, indicating that there was an error in the selection message. The host

must send a complete new selection message (i.e. it may not re-enter after STX)

NO RESPONSE

The selection message was not recognised.

3.1.2 ASCII

This mode is intended for use with simple micros, or ‘dumb’ terminals, which are unable to transmit ASCII control

characters and / or having no hardware handshake. The non-printing control codes are replaced with ‘printing’ charac-

ters as shown in table 3.1.2 below. BCC is omitted, since it might easily be one of the control codes 22 to 26 or 28.

XON/XOFF handshaking is supported. In all other respects, the protocol is the same as the ANSI mode, described

above.

Table 3.1.2 Printing and non-printing codes

Start of text

End of text

End of transmission

Enquiry

Acknowledge

Negative acknowledge

STX

ETX

EOT

ENQ

ACK

NAK

2

3

4

5

6

15

"

#

$

%

&

(

22

23

24

25

26

28

Control character definition

ANSI

standard

character

Hex

code

Hex

code

Printing

character

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Page 17

3.2 PARAMETER ADDRESSING

The protocol uses a three element address: Group Address (G) (0 to 7), set up in the communications configuration to

identify one of up to eight recorders on a multi-drop link; Logical Unit Address (U) and Channel Address (CA). The

recorder can have up to 16 logical units (LUs) associated with it according to the model number. LU 0 is used to ac-

cess instrument, alarm and control mnemonics. In such cases, the channel address is irrelevant, but a valid CA (0 to

F) must still be included in the polling/selecting messages.

As can be seen from table 3.2 below, logical units can have up to 16 associated channel addresses (CAs). For exam-

ple, to access Measuring Channel 28, the logical unit address (U) would be 7, and CA would be 3. To access De-

rived Channel 28, the LU address would be ‘C’ and the CA would be 3.

Table 3.2 Logical unit and channel addresses

3.3 DATA FORMATS

Current recorder protocol specifies a variable number of data bytes, according to the parameter being accessed. Three

basic formats are used:

3.3.1 Hexadecimal (Hex)

Five data bytes are transmitted in the form >HHHH where > must always be present, followed by four hex bytes (H in

the example). The data transferred may represent a single parameter, or a group of parameter values packed into a 16-

bit word and then Hex encoded.

3.3.2 Decimal (Floating point)

Five data bytes are transmitted in on of the following formats according to decimal point position and whether the

value is positive (use decimal point) or negative (use – sign).

DDDD. DDDD–

DDD.D DDD–D

DD.DD DD–DD

D.DDD D–DDD

.DDDD –DDDD

3.3.3 Character

A string of hex data bytes, the number of bytes being defined for each relevant parameter.

1 2 3 4 5 6 7 8 9 A B C D E F

0 1 5 9 13 17 21 25 29 D1 D9 D17 D25 D65 D73 D81

1 2 6 10 14 18 22 26 30 D2 D10 D18 D26 D66 D74 D82

2 3 7 11 15 19 23 27 31 D3 D11 D19 D27 D67 D75 D83

3 4 8 12 16 20 24 28 32 D4 D12 D20 D28 D68 D76 D84

4 33 36 39 42 45 48 51 54 D5 D13 D21 D29 D69 D77 D85

5 34 37 40 43 46 49 52 55 D6 D14 D22 D30 D70 D78 D86

6 35 38 41 44 47 50 53 56 D7 D15 D23 D31 D71 D79 D87

7 57 66 75 84 93 D8 D16 D24 D32 D72 D80 D88

8 58 67 76 85 94 D33 D41 D49 D57 D89 D97

9 59 68 77 86 95 D34 D42 D50 D58 D90 D98

A 60 69 78 87 96 D35 D43 D51 D59 D91 D99

B 61 70 79 88 D36 D44 D52 D60 D92

C 62 71 80 89 D37 D45 D53 D61 D93

D 63 72 81 90 D38 D46 D54 D62 D94

E 64 73 82 91 D39 D47 D55 D63 D95

F 65 74 83 92 D40 D48 D56 D64 D96

LOGICAL UNIT ADDRESS (U)

CHANNEL ADDRESS (CA)

Page 18

HA246958

Issue 14 Mar 02

COMMUNICATIONS MANUAL

3.4 MNEMONICS

The tables which follow, give an alphabetic list of mnemonics with definitions, formats etc. in the following groups.

All mnemonics must be in CAPITAL letters. 4001 mnemonics which are not emulated are not included in the tables.

In such cases, selection will be ignored, and polling will always return the value 0.

Channel mnemonics (see table 3.4.1)

CF Channel flags *

CJ External CJ temperature.

DH Output signal high value.

DL Output signal low value.

EU Engineering units and print zone.

FH Function high value.

FL Function low value.

IL Input signal low value.

IH Input signal high value.

LG Legend string.

LN Legend number.

MV Measured value in hex.

NA Number of alarms assigned.

OC Constant output value

OF Offset value

OH Scale high value.

OL Scale low value.

OS Output source configuration

†

PV Process variable (Measured value scaled to engineering units).

SH Shunt value.

ST Channel status.

Alarm mnemonics (see table 3.4.2)

A1 Alarm type, hysteresis, average.

A2 Alarm sense, alarm status, rate-of-change alarm period.

A3 Set point as a proportion of channel scale.

A4 Deviation, rate-of-change change value.

Instrument mnemonics (see table 3.4.3)

BN Batch number

CS Chart speeds A and B (See also IF)

DY Day number

ER Serial link communications errors

HR Hours

IF Instrument flags (Current chart speed, Date format, Internal CJ units)

II Instrument identifier

IS Instrument alarm and printer on/off-line flags

L1/2/3 User linearisation tables

MI (Not M1) Minutes

MO Month number

M2/3 Mode 2(3) log interval A

PM Print mode

(Continued)

* Channel Flags are:

CJ type Scale print enable

Function engineering units Scale type

Interpolation enable Trace skip

Linearisation (function) type Output type

†

Output source configuration contents:

Error drive Source Channel number

Source type Value format

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