Honeywell Touchpoint 4 User manual

Touchpoint 4 Serial Communication Protocol Issue 1 09/07
Touchpoint 4
Serial Communication Protocol

Touchpoint 4 Serial Communication Protocol Issue 1 09/07
CONTENTS
INTRODUCTION 1
OVERVIEW 1
GLOSSARY 2
COMMUNICATION PORT 2
ADDRESS SETTING PROCEDURE 3
PROTOCOL SPECIFICS 3
Packet Length 4
Checksum 4
ACK/NAK Handshake 5
TIME DIAGRAM 6
PROTOCOL PACKET DEFINITION 6
PACKET FORMAT 6
Start Code 6
Slave Address 6
Length 6
Command 6
Data 7
Checksum 7
GENERIC DATA FORMATS 7
Date Format 7
Time Format 7
Date/Time Examples: 7
Concentration Code: 7
Concentration Data Format Code 8
Concentration Example: 8
GENERIC RESPONSES 8
ACK - 0x01 8
NAK - 0x21 9
Bad Packet - 0x66 9
Unknown CMD –0x67 9
PROTOCOL COMMAND DEFINITION 9
 HANDSHAKECOMMAND–0X40      9
Command packet to instrument: 9
Example: 9
Response packet from instrument: 9
Example: 9
 GETUNITANDPOINTSSTATUS-0X30     10
Command packet to instrument:10
Example:10
Response packet from instrument: 10
Example: 11

Touchpoint 4 Serial Communication Protocol Issue 1 09/07
 RESETFAULT&ALARM–0X41      12
Command packet to instrument: 12
Example: 12
Response packet from instrument: 13
Example: 13
PHYSICAL LAYER 13
PREAMBLE 13
ELECTRICAL INTERFACES 13
Multipoint Serial Bus Infrastructure 13
Multipoint System requirements 14
MECHANICAL INTERFACES 15
Connectors pin-out 15

Touchpoint 4 Serial Communication Protocol Issue 1 09/07
1
Introduction
Overview
This manual describes the setup and operation of the Touchpoint 4 Serial
Communication protocol.
Your Touchpoint 4 gas detector controller is equipped with a serial remote device
communication port. With this communication port, you can monitor the Touchpoint 4
system’soperationwithmasterfromaremotelocation.Itwillalsoallowyoutogather
gas concentration data for analysis or reports.
The Touchpoint 4 gas detector controller accepts commands and issues responses to
any valid command it receives. The Touchpoint 4 gas detector controller is always the
“slave”device,andtheremoteequipmentisthe“master”device.Themastercanbea
personal computer (PC), a programmable logic controller (PLC), or other device capable
ofRS-485serialcommunications.Thiscongurationrequiresa“master”device.
Therefore, one Touchpoint 4 gas detector controller will not communicate directly with
another Touchpoint 4 gas detector controller. However, one master can be used to
communicate with more than one Touchpoint4 gas detector controllers on a two-wire
RS-485 bus.
The Touchpoint 4 gas detector controller supports multiple baud rates. These user
selectableratesare1200,2400,4800,9600,and19,200.Additionalportsettingsare
8-bit, 1 stop bit, and no parity.
TheslaveisidentiedbyanaddressconguredintotheTouchpoint4gasdetector
controller (selectable 1-16). Each Touchpoint4 gas detector controller on an RS-485
network must have a unique address.
Themasterisalwaysataddress0.EachTouchpoint4gasdetectorcontrollerwill
respond to a signal directed to it from the master. To prevent a collision of messages, the
master must avoid transmitting any information after a packet until the slave responds.
Touchpoint4willrespondin500ms.

Touchpoint 4 Serial Communication Protocol Issue 1 09/07
Glossary
The following terms are used in this manual:
Handshake: The process of acknowledging a communication has been received.
The Touchpoint4 gas detector controller uses ACK/NAK responses.
Hexadecimal: A type of numbering system with a base of 16. In this numerical system,
thelettersAthroughFrepresentsnumbers10through15respectively.Forexample,
3Finhexadecimalrepresents63indecimal.Theshortenedversionoftheword
hexadecimalisgenerally"Hex",asin"Hex3F.""0x"isthenotationusedinthismanual
forhexadecimal(e.g.0x3F).
Instrument: This term is used to refer to the Touchpoint4 gas detector controller.
Master: A computer or PLC that communicates with slaves using the
Touchpoint4 protocol.
Packet: A block of information that is passed between the master and the slave.
A packet is made from many bytes of information.
Protocol: The manner in which data is transferred and the format used for the transfer.
Touchpoint4 protocol refers to the packets of transferred data the Touchpoint4
instrument recognizes.
Slave: Touchpoint4 gas detector controller. A network may have several slaves.
Time-Out:Themaximumamountoftimeallowedbetweenthetimethelastbyteofa
packetissentfromthe“master”devicetothetimethe“slave”deviceresponds.
The time-out period of 1 second is recommended for this protocol. In fact, the period
fromrequesttransmissiontoresponsereceptionisnotmorethan500ms.
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Communication Port
Access to the Touchpoint4 protocol is through the terminal block on the common
module of Touchpoint4 gas detector controller. This port is designed for bidirectional
communications between the Touchpoint4 instrument and your master.
Signals present at the port conform to RS-485 specifications. The pin-out specifications
are described in the chapter connectors pin-out.
Address Setting Procedure
After the networking cabling has been connected to the slave, the slave must be
configured to communicate. Baud rate and address are selectable. Configuration is
performed with the following sequence:
1. Access the menu system and select the RS485 communication link
settings menu option. Press UP/DOWN, the icon flashes.
 2. PressOK,thecontroller’scurrentaddressisdisplayed.
3. Use UP/DOWN to change the address (between 1 and 16 available).
4. Press OK to accept the change.
The display changes to display the current baud rate.
 5. UseUP/DOWNtochangethebaudrate(1200,2400,4800,9600,
  19200available).
6. Press OK to accept the change.
Please refer to the Technical Manual for more details.
Protocol Specics
Theprotocolhasbeendesignedforflexibilityandefficiency.Thisbyte-wiseprotocol
communicates information by transferring bytes of data back and forth between master
and slave. A group of bytes for each communication is called a packet.
The master and slave(s) transfer information via data packets. These packets will always
contain bytes to start communication, an address, a length, a command, one or more
data and a checksum.
Additional optional variable-length data bytes or optional parameters can also be sent
or received. This section is a brief overview of the protocol specifics.
Packet Length
Just as all words are not the same length (number of letters), packets may also vary in
length. In this protocol, the length of command and data field is put before command
fieldinthepacket.Yourdatacontaining"0x42,0x41,0x44"willthenbecome“0x03,
0x42,0x41,0x44”.

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Checksum
During transmission of the packet, an error could change the value of the data.
Supposeinourexample,forinstance,thepacket0x03,0x42,0x41,0x44isactually
0x03,0x42,0x30,0x44.Howcanyoudeterminethatthenumbersyougetarethesame
as the numbers sent?
Touchpoint4serialcommunicationprotocolusesaXORcheck-characterasamethodof
assigning a value to the packet to check if any of bytes have been modified.
IfallthedatabytesareXOR-edtogetherandthischeckmadeintoabyte,thisbyte
could be called a checksum character. For the Touchpoint4, the checksum is the bit-
wiseXORresultofallthebytesinthepacket.Inourexample,thepacketis0x03,
0x42,0x41,0x44.Forthispacket,theXORresult0x44ofallthebytesaddedtothe
checksummustbezero(0).Anyotherresultindicatesthereisanerrorwiththedata.
It is usually important for the master to thoroughly check data coming from the slave
for validity before accepting it. This is because in many installations, an alarm from the
Touchpoint4 indicates severe danger to life and property. The master's determination
thatanalarmexistsmaystimulateavigorousandpossiblyexpensivehumanresponse.
Therefore it is important to avoid false alarms. The master should reject any packets
that contain an invalid start character, an invalid address, an invalid length byte or
an invalid checksum. Otherwise the probability of an evacuation because of simple
network noise is unnecessarily large.
The actual data in the packet is interpreted in a somewhat different manner from our
previousexamples.Boththemasterandtheslavecommunicateusingthepacket
format in Figure 2. It contains a start code, an address, a length, a command and its
associateddata,andachecksum.Thestartcodeisfixed.Theaddressistheslave
addressregardlessofthepacket’sorigin.Thelengthindicatesthenumberofbytesof
command and data field. The command indicates what type of information is being
transmittedinthepacket.TheDatafieldisnullinsomecases.Ifexist,itcontains
specificargumentsorvaluestobeinterpreted.ThechecksumisXORresultofall
previous bytes.
ACK/NAK Handshake
Each slave (Touchpoint4) uses a handshake scheme between itself and the master.
The simplest response back from the instrument is called an ACK (an abbreviation for
ACKnowledge).Whentheslavereceivesthehandshakecommand(0X40)packetfrom
themaster,itwillsendbackanACKresponse.TheACKresponsewillbe0x01followed
bythehandshakecommand0x40(see Handshake command).
If however, the checksum does not match, the slave will send a NAK (an abbreviation
for Negative AcKnowledge). A NAK indicates that a data packet has been received, but
the checksum did not match with the packet data.
Themastermaysendtherequestagain.AnexampleofanACKpacketis0x7F,0x01,
0x02,0x40,0x01,0x3D(7FXOR01XOR02XOR40XOR01=0x3D).
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Touchpoint 4 Serial Communication Protocol Issue 1 09/07
Time diagram
Figure 1. Communication time diagram
Protocol Packet Denition
Packet Format
The format of packets using Touchpoint4 SERIAL COMMUNICATION PROTOCOL is as
follows:
Figure 2. Protocol packet format
Start Code Size:1byte.Always0x7F.
Slave Address Size: 1 byte.
Represents the Touchpoint4 gas detector controller address,
   0X01to0X10(1to16decimal).
Length Size: 1 byte.
The number of bytes in the Command field and Data field.
The total packet length is 4 bytes larger than this.
Command Size: 1 byte.
   Thisis0x30,0x40or0x41asdefinedintheremainderofthisbook.
Data  Size:0-250byte(s).
This section varies according to the chosen command and may
be omitted.
Checksum Size: 1 byte
   Thebit-wiseXORresultofallthepreviousbytesinthepacket.
   ThismakestheXORoftheentirepacket0X00.
Start
Code
Slave
Address
Length Command Data Checksum
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Touchpoint 4 Serial Communication Protocol Issue 1 09/07
Generic Data Formats
Date Format 2 bytes.
Bit: 1598540
Year Month Day
Figure 3. Data format
Year: (7 bits)
Month: (4 bits)
Day: (5 bits)
   Yearisbasedfrom1980.1989wouldbe1989-1980=9.
Time Format 2 bytes
Bit: 151110540
Year Month Day
Figure 4. Time format
Hours: (5 bits)
Minutes: (6 bits)
Seconds: (5 bits)
   Secondsalwaysbe0.
Date/Time Examples:
Date: 1F 56 Oct. 22. 1995
Date: 1F 75 Nov. 21, 1995
   Time:13C0 02:30:00
   Time:7400 14:32:00
   Time:4700 08:56:00
Concentration Code:
2 bytes
Bit: 15870
H L
Figure 5. Concentration code format
   Forexample,(HEX)013Drepresentsthevalueis317.
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Touchpoint 4 Serial Communication Protocol Issue 1 09/07
Concentration Data Format Code
   UUXXXYYY
UU Unit
    UU=00ppm
    UU=01%LEL
    UU=10%V/V
    UU=11kppm
   XXX reserved
YYY decimal place
    YYY=000 nodecimalplaces
    YYY=001 1decimalplace
    YYY=010 2decimalplaces
    YYY=011 3decimalplaces
Forexample,(HEX)81(10000001)represents%V/Vwith1decimalplace.
Concentration Example:
Foraconcentrationvalue(HEX)0062,98decimal,FormatCodeInterpretation:
  00000000(00) 98ppm
  10000001(81) 9.8%V/V
  01000000(40) 98%LEL
Generic Responses
There are four generic responses. Each of these response packets is 6 bytes, and
contains the start byte, address, length, command code, ACK/NAK code and
Checksum. All ACK/NAK code is sent following the command code in the last
received packet.
ACK - 0x01
This is used for an acknowledgement of the handshake command.
NAK - 0x21
This is used for a negative acknowledgement of packet if the last received packet had
an incorrect checksum.
Bad Packet - 0x66
This is sent to the master when the start byte or length in the last received packet
is incorrect.
Unknown CMD –0x67
This response is sent by the slave when a command is not recognized.
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