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- Page 1 Serial Communication Protocol Touchpoint 4 Serial Communication Protocol Issue 1 09/07 Touchpoint 4...
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Page 2: Table Of Contents
Touchpoint 4 Serial Communication Protocol Issue 1 09/07 CONTENTS INTRODUCTION OVERVIEW GLOSSARY COMMUNICATION PORT ADDRESS SETTING PROCEDURE PROTOCOL SPECIFICS Packet Length Checksum ACK/NAK Handshake TIME DIAGRAM PROTOCOL PACKET DEFINITION PACKET FORMAT Start Code Slave Address Length Command Data Checksum GENERIC DATA FORMATS Date Format Time Format Date/Time Examples: Concentration Code:... - Page 3 Touchpoint 4 Serial Communication Protocol Issue 1 09/07 RESET FAULT & ALARM – 0X41 Command packet to instrument: Example: Response packet from instrument: Example: PHYSICAL LAYER PREAMBLE ELECTRICAL INTERFACES Multipoint Serial Bus Infrastructure Multipoint System requirements MECHANICAL INTERFACES Connectors pin-out...
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Page 4: Introduction
Touchpoint 4 Serial Communication Protocol Issue 1 09/07 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 configuration 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 identified by an address configured 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. -
Page 5: Glossary
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. -
Page 6: Communication Port
Touchpoint 4 Serial Communication Protocol Issue 1 09/07 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. -
Page 7: Checksum
Touchpoint 4 Serial Communication Protocol Issue 1 09/07 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. -
Page 8: Time Diagram
Touchpoint 4 Serial Communication Protocol Issue 1 09/07 Time diagram Figure 1. Communication time diagram Protocol Packet Definition Packet Format The format of packets using Touchpoint4 SERIAL COMMUNICATION PROTOCOL is as follows: Start Slave Length Command Data Checksum Code Address Figure 2. Protocol packet format Start Code Size: 1 byte. Always 0x7F. Slave Address Size: 1 byte. -
Page 9: Generic Data Formats
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... -
Page 10: Concentration Data Format Code
Touchpoint 4 Serial Communication Protocol Issue 1 09/07 Concentration Data Format Code UUXXXYYY 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... -
Page 11: Protocol Command Definition
Touchpoint 4 Serial Communication Protocol Issue 1 09/07 Protocol Command Definition Handshake command – 0x40 This is used to test for communication between the master and the specified slave. Command packet to instrument: Command code: 0x40 Data field: null Checksum: 1 byte Example: If the master wants to test the communication with the addressed 01 instrument, it should send out: 0x7f 0x01 0x01 0x40 0x3f. Response packet from instrument: Command code: 0x40 ACK code: 0x01 Checksum: 1 byte... -
Page 12: Example 1
Touchpoint 4 Serial Communication Protocol Issue 1 09/07 Unit fault status: 1 byte 0x00: no fault 0x01: line circuit fault 0x02: negative draft 0x03: in DC2 AC fault 0x04: in DC2 DC low voltage 0x05: in DC2 DC fault Channel(s) status: 6 * n bytes (n = quantity of channels) Every channel status has 6 bytes, defined as following: Channel number: 1 byte (1 to 4) Concentration format: 1 byte Concentration: 2 bytes Channel alarm status: 1 byte (refer to unit alarm status) Channel fault status: 1 byte (refer to unit fault status) Checksum: 1 byte Each channel status data contains 6 bytes, so the length field of the response packet depends on the quantity of the channel of Touchpoint4. For example, if there are 4... - Page 13 Touchpoint 4 Serial Communication Protocol Issue 1 09/07 Example 2: 0x7f 0x01 0x13 0x30 0x1f 0x56 date: OCT. 22, 1995 0x13 0xc0 time: 02:30:00 0x01 alarm: A1 alarm 0x00 fault: no fault 0x02 channel number: 2 0x81 0x00 0x62 concentration: 9.8 %V/V 0x01 alarm: A1 alarm 0x00 fault: no fault 0x03 channel number: 4 0x81 0x00 0x62 concentration: 9.8 %V/V 0x01 alarm: A1 alarm 0x00 fault: no fault 0xC7 checksum The example means this Touchpoint4 gas detector controller has two channels connected, Channel 2 and Channel 4.
- Page 14 Touchpoint 4 Serial Communication Protocol Issue 1 09/07 Reset fault & alarm – 0x41 This command allows a remote reset of latched visual, audio and relay outputs resulted from an alarm or fault. Command packet to instrument: Command code: 0x41 Data field: null Example: If the master wants to reset latched outputs of addressed 01 instrument, it should send out: 0x7f 0x01 0x01 0x41 0x3e Response packet from instrument: Command code: 0x41 Data field: null Example: The addressed 01 instrument receives the reset fault & alarm command and responses: 0x7f 0x01 0x01 0x41 0x3e...
- Page 15 Touchpoint 4 Serial Communication Protocol Issue 1 09/07 PHYSICAL LAYER Preamble The physical layer of Touchpoint4 serial communication protocol is an electrical interface in accordance with EIA/TIA-485 standard (also known as RS485 standard). In Touchpoint4 serial communication system, a Master Device and one or several Slave Devices communicate on a balanced twisted pair, on which bi-directional data are transmitted, at the bit rate as user configured. Electrical Interfaces Multipoint Serial Bus Infrastructure Touchpoint4 Serial Communication system implements a “Two-Wire” electrical interface in accordance with EIA/TIA-485 standard. On such a 2W-bus, at any time only one driver has the right for transmitting. The following figure gives a general overview of the serial bus infrastructure in Touchpoint4 Serial Communication system. Figure 6. Communication infrastructure The Touchpoint4 gas detector controllers are connected directly to the trunk cable. The master, PC or PLC, is connected directly or via a derivation, according to the master instruction. The cable should be shielded. Note: the Touchpoint4 RS-485 interface is not electrically isolated. A common mode voltage of 7 volt or greater between any two nodes on the network will interfere with communications. Proper earthing of every Touchpoint4 and the Master is essential. Multipoint System requirements...
- Page 16 Touchpoint 4 Serial Communication Protocol Issue 1 09/07 Topology Touchpoint4 Serial Communication system has one trunk cable, along which devices are connected, directly (daisy chaining) or by short derivation cables. The trunk cable, also named “Bus”, can be long (see hereafter). Its two ends should be connected to Line Terminations. Length The end-to-end length of the trunk cable must be limited. The maximum length depends on the baud rate, the cable (Gauge, Capacitance or Characteristic Impedance), and the quantity of loads on the daisy chain. For a maximum 9600 Baud Rate and AWG26 (or wider) gauge, the maximum length is 1000m. If the derivation cable is needed for the connection of the master, the derivation must be short, never more than 20m. Grounding Arrangements At one end of each cable its shield must be connected to protective ground. Line Termination To minimize the reflections from the end of the RS485-cable, it is recommended to place a Line Termination near each of the 2 Ends of the Bus. It is important that the line must be terminated at both ends since the propagation is bi-directional, but it is not allowed to place more than 2 LT on one passive D0-D1 balanced pair. Never place any LT on a derivation cable. Each line termination must be connected between the two conductors of the balanced line: D0 and D1. Line termination may be a resistor of 100 ohms to 150 ohms (0.5 W). Pull-up and Pull-down Resistors Line control has been implemented in Touchpoint4 gas detector controller so that the bus contains a valid "off" signal when no node is transmitting. No external pull-up or...
- Page 17 Touchpoint 4 Serial Communication Protocol Issue 1 09/07 Mechanical Interfaces Connectors pin-out The following figure shows the pin-out on the terminal block of Touchpoint4 gas detector controller. Figure 7. Touchpoint4 communication pin-out...
- Page 18 Touchpoint 4 Serial Communication Protocol Issue 1 09/07 Find out more www.honeywellanalytics.com Contact Honeywell Analytics: Europe, Middle East, Africa Life Safety Distribution AG Wilstrasse 11-U11 CH-8610 Uster Switzerland Tel: +41 (0)44 943 4300 Fax: +41 (0)44 943 4398 [email protected] Americas Honeywell Analytics Distribution, Inc.