Atest Gaz PW-033-B, User Manual

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2.4 ExBUS communication port – data gateway, External Data Inputs
The Control Unit Module Sigma MOD LCD comprise a communication port called ExBUS designed for
exchange of information between the Sigma Gas system and external environment (e.g. PLCs, SCADA, etc.).
The port is bidirectional and can be used both to read information about current status of the Sigma Gas
system e.g.:
statuses of detectors,
measured concentration values,
state of PK outputs and DI inputs.
It is also possible to affect operation of the system by means of dedicated digital inputs. Purpose of those
inputs is exactly the same as in case of DI lines outlined in Section 2.2.
The port can be also used to receive commands issued by a system operator, e.g. reset a locked detector.
See details in Attachment [4].
Exchange of information is carried out by means of the RS-485 digital link and MODBUS
2 protocol, where
the control unit module operates as a SLAVE device. The mentioned functionalities are implemented as read
and write operations for registers from the address space of ‘holding registers’ in the control module. The
following settings for the MODBUS protocol are available:
variant of the MODBUS ASCII and MODBUS SCU protocols
network address of the device from 1 to 255 ( 20 ),
transmission rate: 4,800, 9,600, 19,200 , 38,400, 57,600 or 115,200 bauds,
parity check: (N) none, ( E ) even, (O) odd,
frame format (only for MODBUS ASCII) 7 or 8 data bits.
The foregoing settings can be adjusted by a user from the level of the control menu (see Section 3.8.6).
The map of the control unit memory is shown in Attachment [4].
The default configuration of External Data Inputs is shown in the table below:
Bit Flags Description Default configuration
0 External_DI_0 Input no. 0 Deactivation of an internal buzzer
1 External_DI_1 Input no. 1 Deactivation of an external sound warning device (siren)
2 External_DI_2 Input no. 2 Reset of a locked optic /light warning device
3 External_DI_3 Input no. 3 Activation of an alarm
4..15 External_DI_4..15 Input no. 4..15 Not assigned
Table 5: Default configuration of External DI input
The desired functionalities for that port must be specified upon submission of the order
(both the transmission protocol and assignment of External Digital Inputs to specific
functions).
The port is sensitive to polarity of transmission lines – see details in Section 2.5. Example waveforms with
standard settings for External Data Inputs (ExDI) are shown in Figure 6 and 7.
2 Default settings are bolded.
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User Manual: POD-003-ENG R04