6
-114
n
Communications
Response
Time
The
communications response times for communications with an Inverter via the RS-422/485 port of an
Omron-made
Communications Board are detailed below. Use this information as a reference when deciding
the
number of Slaves to be connected to one network, and when considering the timing of input and output
signals.
Communications
Time
for
One
Message
A
wide variety of programs for RS-422/485 communications can be created using the protocol macro func-
tion.
The communications times will vary according to the contents of the program.
In
general, the communications time for one message can be calculated using the following formula.
Calculation
Example
The
communications time required for one Slave in the protocol macro created
under
Creating a Project File
,
can
be
calculated according to the following formula. (Baud rate = 19,200 bps.)
If
there are N Slaves, the total communications time will be N x 81.2 ms. Consequently, the more Slaves that
are
used, the longer the communications time will be. If the number of Slaves is too high, it is possible that the
detection
time of 2 s for communications time-over will be exceeded. In this case, either disable the time-over
detection
function and use a different sequence to detect communications errors, or increase the number of
Masters
thereby decreasing the number of Slaves per Master.
Communications
time = [Number of bytes in DSR message x 10 (See note 1.) x (1/baud rate) x 1,000 (ms)]
+
[Number of bytes in response x 10 x (1/baud rate) x 1,000 (ms)] + [24 x (1/baud rate) x 1,000 (ms)] + send
wait
time setting (ms) + protocol macro waiting time (See note 2.) (ms)
The
reason that the number of bytes in the DSR message and response is multiplied by 10 is because both the
start
bit and the stop bit require one bit each.
(1
byte = 8 bits) + (start bit: 1 bit) + (stop bit: 1 bit) = 10 bits
With
RS-422A/485 communications, set at least 20 ms as the protocol macro waiting time.
Communications
time = [DSR message to write data (13 bytes) + DSR message to read (8 bytes)) x 10 x (1/
19,200)
x 1,000 (ms)] + [write response (8 bytes) + read response (7 bytes)) x 10 x (1/19,200) x 1,000 (ms)]
+
[24 x (1/19,200) x 1,000 (ms) x 2] + [10 (ms) x 2] + [20 (ms) x 2] = 81.2 (ms)
Summary of Contents for SYSDRIVE 3G3RV
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