Operating manual ВІСТ.418266.006-03 НЕ
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APPENDIX B
COMMUNICATIONS PROTOCOL OF THE DATA DISPLAY SYSTEM AND
THE DETECTING UNIT
B.1 Data frames exchange between the detecting unit and the data display system is done via
RS-485 interface in a half-duplex mode.
Exchange parameters:
- rate: 19,200 bps;
- data word length: 8 bit;
- parity bit: none;
- stop bit: 1.
Time interval between the bytes in one frame should not exceed 1 ms. Time interval between
the frames should not be less than 5 ms.
B.2 After the supply voltage from the data display system is applied to the detecting unit, the
latter starts automatic gamma radiation DER measurement not later than in 30 s and processing of
data frames form the data display system.
B.3 This detecting unit supports data communications protocol version with both 4-digit address
field (v1.2), and 8-digit address field (v1.3).
B.3.1 Communications protocol with the 4-digit address field (v1.2).
To receive the measured value of DER from the detecting unit, the data display system should
transmit the
“DER query”
frame to the detecting unit. The detecting unit will respond in 5 ms to
15 ms with the
“Current DER
” frame, where current DER, maximum statistical error of its
measurement, and self-testing results of the detecting unit will be displayed.
To receive the measured value of temperature from the detecting unit (with embedded
temperature detector), the data display system should transmit the
“Temperature query”
frame to
the detecting unit. The detecting unit will respond in 5 ms to 15 ms with the
“Current
temperature
” frame, where current temperature and condition of the temperature detector will be
given.
To receive the current calibration factors from the detecting unit, the data display system should
transmit the
“Current factors query”
frame to the detecting unit. Within 500 ms the detecting unit
will respond with the
“Factors”
frame, where the current calibration factors will be given.
To change the calibration factors, the data display system should transmit the
“New factors”
frame to the detecting unit. Within 500 ms the detecting unit will respond with the “
Confirmation
of factors”
frame with the displayed results of calibration factors reception. In the event of
successful reception, the detecting unit records them in the nonvolatile memory, and, not later than
in 30 s, starts measurement of gamma radiation DER using new factors.
To receive the serial number of the detecting unit, the data display system should transmit the
“Serial # query”
frame to the detecting unit. The detecting unit will respond in 5 ms to
15 ms with the
“Serial #”
frame
with the displayed
serial number.
To change the address of the detecting unit, the data display system should transmit the
“Address change”
frame to the detecting unit. In 5 ms to 500 ms the detecting unit will respond
with the
“Confirmation”
frame.
Important!
In the address field of the
“Confirmation”
frame the old value of address will be
recorded. In the event of successful reception of a new value, the detecting unit records it in the
nonvolatile memory, and not later than in 5 s starts responding to the frames with a new address.
To make operation with several detecting units (up to 15 units) easier that are simultaneously
connected to the data display system via single RS-485 interface, the
0Fh
broadcast address is
provided. The use of this address is permitted only in the
“DER query”
,
“Temperature query”
and
“Serial # query”
frames. All detecting units respond to the query with such address (broadcast
query).
When the detecting units respond to the broadcast query, each of them does it with delay T,
which is calculated by the formula:
T = 5mS + Adr * 8mS,
(B.1)
where Adr is the detecting unit’s address.
The broadcast query also enables easy autodetection of the detecting units that
connect/disconnect to/from the data display system in the process of system operation.