Advertisement
B.3.2 Communications protocol with the 8-digit field address (v1.3).
To receive the measured value of DER from the detecting unit, the data display system should
transmit the "DER1 query" frame to the detecting unit. The detecting unit will respond in 5 ms to
15 ms with the "Current DER1" 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 "Temperature1 query" frame to the detecting
unit. The detecting unit will respond in 5 ms to 15 ms with the "Current temperature1" frame,
where current temperature and condition of the temperature detector will be transferred.
To receive the serial number of the detecting unit and the response delay factor to broadcast query,
the data display system should send the "Serial #_1 query" frame to the detecting unit. The detecting
unit will respond in 5 ms to 15 ms with the "Serial #_1" frame with the displayed serial number and
the response delay factor to the broadcast query.
To change the address of the detecting unit and the response delay factor to the broadcast query,
the data display system should transmit the "Address1 change" frame to the detecting unit. In 5 ms
to 500 ms the detecting unit will respond with the "Confirmation1" frame. Caution! In the address
field of the "Confirmation1" frame the old value of address will be recorded. In the event of
successful reception of a new value and response delay factor to the broadcast query, the detecting
unit records it in the nonvolatile memory, and not later than in 5 s starts responding to frames with a
new address.
To make operation with several detecting units (up to 255 units) easier that are simultaneously
connected to the data display system via single RS-485 interface, the 0FFh broadcast address is
provided. The use of this address is permitted only in the "DER1 query", "Temperature1 query"
and "Serial #_1 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:
if the response delay factor to the broadcast query t is within the range from 0 to 15;
or by the formula:
if the response delay factor to the broadcast query t is within the range from 16 to 255.
The broadcast query also enables easy realization of autodetection of the detecting units that
connect/disconnect to/from the data display system in the process of system operation.
T = 5 mS + t × 8 mS,
T = (5 mS + t × 8 mS) + 125 mS ,
30
(B.2.1)
(B.2.2)
Advertisement
