DESCRIPTION The Modbus interface unit connects to the RS-485 peripheral bus of a fire control panel and allows panel interrogation by a Modbus control system. Information on the states of panel outputs, peripherals, detectors and the general operating condition of the panel can be requested. INDICATOR LED’s
EARTH TERMINATION POINT
POWER CONNECTIONS
CN418
RS-485 (to panel)
- EXP-057
Page 1 of 7 -
RS-232 (to Modbus)
INSTALLATION The unit consists of a circuit card mounted on a steel plate within a polycarbonate IP67 rated enclosure, as shown above. Pre-pressed knock-outs on the box sides allow cable entry glands to be fitted for power and communication line wiring. A small plug in RS-232 card provides a communication link to the Modbus controller, jumper J1 on the card should be fitted in position A. A DC supply in the range of 18-28V, typically 24V, rated at 150mA, is required to power the interface, An on board switch mode power supply isolates this input from all communication circuitry. An adequate DC supply can be obtained from the fire control panels auxiliary 24V output (see fire control panel manual). An earth reference should be connected to the Modbus Interface Platforms Earth termination point from the supply earth (i.e. fire control panel entry gland). A block diagram of the typical wiring arrangement is shown below.
MODBUS INTERFACE PLATFORM
B A B A
485 CARD
0v 0v E 24v 24v
A B E A B
MODBUS MASTER CONTROLLER
RS-232 CARD GND RX TX RTS
PORT ‘D’
FIRE CONTROL PANEL
(Data Direction)
The RS-485 signal cable should be a twisted pair safety cable type which conforms to BS6387. The earth lead of this cable should be suitably Earth referenced at the fire control panel entry gland and at the Modbus interface platforms Earth termination point or at the RS-485 Earth termination connector. The signal pair should be connected ‘A’ to ‘A’ and ‘B’ to ‘B’.
COMMISSIONING The eight way DIL defines both the interfaces Morley peripheral address and its Modbus slave address. Valid addresses are in the range 1 to 126. The auto-learn option in the panel configure - peripherals menu should be used to detect the presence of the interface unit, it will register under ‘other’ when found. By selecting the device option in the configure - peripherals menu the interface will be displayed as type Modbus as shown below, P:005 Modbus
Z001-”Reception S= nn
”
The number nn represents status information of interface communications, it can take the following values:
CN418
- EXP-057
Page 2 of 7 -
Signal (nn) 0 1 16
MODBUS MASTER
TO
Description No communication with interface unit Communicating with interface / Received Modbus query Communicating with interface unit
MODBUS INTERFACE LINK
TESTING
The Modbus communication link between the master and the interface can be verified by sending a query with an unrecognised function code, (see Modbus section later) from the master. The query will be trapped by the interface and an exception directly returned, A suggested test query and its response are: Test query: 01-05-07-D1-00-64-9D-6C 83-50
Reply:
01-85-01-
(Values in italics are CRC checksums)
INDICATOR LEDS’ The Modbus interface has three indicators: LED1 - Blinks at 1Hz when unit is powered and operational. LED2 - Indicates Modbus data is currently being received on the RS232 port which is addressed to the unit. LED3 - Indicates Panel data is currently being received on the RS-485 port which is addressed to the unit.
PANEL SOFTWARE REQUIREMENTS The fire control panel must be running software version 560 or higher to support a Modbus interface unit.
CN418
- EXP-057
Page 3 of 7 -
IMPLEMENTED MODBUS PROTOCOL This section details the Modbus protocol implemented within the interface and the mapping of addresses from Modbus to fire panel.
MODBUS COMMUNICATION SETTINGS Parameter Mode : Baud rate : Data bits : Framing : Parity : Physical Interface :
At the Modbus interface unit the Modbus starting address is translated to a physical device address. The rules defining the translation process are: Sensor Loops: The panel supports a maximum of 128 sensors per loop. The translation process is identical for all sensor loops according to the rule :Modbus Starting Address = Address. e.g.
2000 + ((Loop number - 1) × 200) + Device
Modbus address 2001 = Input on Loop 1 Address 1 2100 = Input on Loop 1 Address 100 2928 = Input on Loop 5 Address 128
Peripherals: The panel supports peripherals addressed up to and including 126. The allocation of peripherals to Modbus addresses is :Modbus address = 3000 + Peripheral Address e.g.
Modbus address 3001 = Input at Peripheral Address 1 3126 = Input at Peripheral Address 126
Outputs Devices: Each fire panel supports as standard 100 individually programmable output devices. These are allocated 100 consecutive Modbus addresses (the fire programming software defines the type of output device). Modbus address = 4000 + Output Device e.g.
Requesting status from addresses not specified in the above table will result in an ‘Illegal data address’ exception being returned from the Modbus interface.
MODBUS FUNCTION COMMANDS The Modbus commands in the following section will be understood and acted upon by the fire panel interface. There will typically be a delay of one second between the interface receiving a request from a Modbus master and it starting to transmit the reply. Read Coil Status: (Read fire panel device output status) Slave Address Function Code Starting Address Hi Starting Address Lo No. of points Hi No. of points Lo (I) CRC Hi CRC Lo
nn 01 AA aa 00 pp
Notes: I.
An exception will result if more than the fire panels current maximum number of supported points are requested.
II. The output output per address is meaning of
device status in the reply field is packed as one bit of the data field. The device at the starting transmitted as the LSB of the first reply byte. The each bit is:
1 = Output Turned On.
0 = Output Turned Off.
Read Input Status: (Read fire panel device input/peripheral status) Slave Address Function Code Starting Address Hi Starting Address Lo No. of points Hi No. of points Lo (I) CRC Hi CRC Lo
nn 02 AA aa 00 pp
Notes: I.
The maximum number of inputs requested in one message is 128 sensors (for Apollo systems) and 126 for peripherals.
II. If more than the fire panels current maximum number of supported points are requested, or the points are not on one loop, an exception will be returned.
CN418
- EXP-057
Page 5 of 7 -
III. The device input status in the reply field is packed as one input per bit of the data field. The device at the starting address is transmitted as the LSB of the first reply byte. The meaning of each bit is: 1 = Input activated
0 = Input in quiescent state.
IV. The input state is latched by the fire panel once it has been activated and will not return to zero until the fire panel is reset (This allows for detectors malfunctioning due to heat damage in a fire situation). Read Input Registers: (Read fire panel detector analogue input) Slave Address Function Code Starting Address Hi Starting Address Lo No. of registers Hi No. of registers Lo (I) CRC Hi CRC Lo
nn 04 AA aa 00 pp
Notes: I.
The maximum number of input registers requested in one message is 64. If this is exceeded then an exception will be returned.
II. If the points are not on the same loop then an exception will be returned. III. The register data contains the analogue signal returned by the device. IV. According to the Modicon specification, two bytes are returned for each register. With Apollo detectors the high-order byte will always be zero, with the low-order byte returning the detector analogue signal. Read Exception Status: (Read Panel Status) Slave Address Function Code CRC Hi CRC Lo
nn 07
The reply consists of a single panel status byte, formatted as follows :0 1 2 3 4 5 6 7
CN418
Bit N0. (LSB)
(MSB)
Significance internal buzzer muted alarms silenced disablement panel in Fire panel in Fault panel in Pre-Alarm panel in test Mode unused
- EXP-057
Page 6 of 7 -
Summary of Recognised Modbus Commands: The table below shows which type of address can be requested using the four recognised Modbus commands. Modbus Function 01 02 04 07
Description
Sensors
Read Coil Status Read Input Status Read Input Registers Read Exception Status
× 9 9 ×
Periphera ls × 9 × ×
Outputs 9 × × ×
Note: Broadcast not supported on any of the commands. An ‘Illegal function’ exception will be returned from the Modbus interface if a function other than those listed above is received. Summary of Possible Exception Codes: The following exception codes can be returned from the Modbus Interface: Exception Code 01 02
Description Illegal function Illegal data address
REFERENCES Refer to Modbus protocol specification in PI-MBUS-300 Rev. E for more details.
