KEYENCE BL-180 - Manual (Page 101)

Power Supply BL-U1
95
5.3 Details on Data Communication
Communication
Procedure
1. Send a polling command (P) to the BL series whose data you wish to
receive.
mmm=008
2. The RS-485 uses a 2-wire cable which sends data and receives data along
the same wire. Therefore, the command sent from the host computer loops
back to the host computer.
In this example, immediately after the above command is sent to the BL se-
ries, the following data loops back to the host computer.
mmm=008
To detect data conflict, compare the command sent from the host computer
with the loopback data.
However, data collision will not occur if you follow the procedure described
here. Normally, you need not compare the command sent from the host com-
puter with the loopback data.
3. When the BL series’ transmission buffer contains any data, the BL series
sends back the read data, and waits for the clear command (C).
When the BL series’ transmission buffer contains no data, the BL series
sends back the following response (e: empty), and does not wait for the clear
command.
When the BL series’ transmission buffer is full, the BL series sends back the
following response (OVER), clears all data stored in the transmission buffer,
and waits for the clear command.
[STX] mmm nn P cc [ETX]
[STX] mmm nn P cc [ETX]
[STX] mmm nn Read Data cc [ETX]
[STX] mmm nn e cc [ETX]
[STX] mmm nn OVER cc [ETX]
S
T
X
E
T
X
008 03 C 78
S
T
X
E
T
X
008 03 C 78
S
T
X
E
T
X
009 03 OK 3E
S
T
X
E
T
X
008 03 P 6B
S
T
X
E
T
X
008 03 P 6B
S
T
X
E
T
X
011 03 1234 37
ID•••1
ID•••4
ID•••3
ID•••2
1
2
3
4
5
6
ID No. 3 is
reading bar code
data ”1234“