KEYENCE N-400 - Manual (Page 92)

Chapter 4 Multi-Drop Link Mode Control Procedure
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From the above data, the RS-485 data transmission time (“A” shown in the timing
chart on the previous page) is obtained as follows:
• Maximum time: A = a x n + b (n = Number of connected BL series)
• Minimum time: A = b
* The above table shows the case in which one BL series sends data to the N-
400. When several BL series simultaneously send data, the required time may
be longer than the above.
The time duration “b” (corresponding to the case in which the BL series has
stored some data) is prolonged.
Next, obtain the time duration required for the RS-232C data transmission.
The RS-232C data transmission time (“B” shown in the timing chart on the previous
page) can be obtained from the following formula:
From the above data, the total communication time is obtained as follows:
Communication time = A + B
■ Command communication time
When you send a command (e.g. Laser ON command) to the BL series, obtain the
time duration for how long it takes for the BL series to receive the command after
you send it to the N-400.
The communication time required to send a command to the BL series consists of
the time required for the RS-232C command transmission from the host computer
to the N-400, and the time required for the RS-485 command transmission from the
N-400 to each BL series.
However, since each BL series constantly sends its data to the N400, the com-
mand transmission from the N-400 to the BL series must be performed in the
interval of the data transmission from the BL series to the N-400.
First, obtain the time (C) required for the RS-232C command transmission from the
host computer to the N-400. Calculate this time duration by substituting the number
of command characters (e.g. LON: three characters, LOFF: four characters) for the
number of data digits in formula B given above.
Baud rate (for RS-232C) Communication time (b)
Number of data Number of data Number of data
digits: 10 digits: 20 digits: 32
9600 bps 21.3 ms 33.8 ms 48.8 ms
38400 bps 5.4 ms 8.5 ms 12.2 ms
B =
Amount of data + (1: Set Parity) + Start/Stop bit
x
Baud rate
(Number of data digits + Header/Delimiter + 5)
N-400
(RS-485)
BL
N-400
(RS-232C)
Host
1 2 3 1 4 2
Command Command
3 5 5 1 2 3 5 1 4 4
D C D C
E E
a b
Command Command