Keyence BL-180 User Manual download pdf (Page 101)

Power Supply BL-U1

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 Read Data cc [ETX]

[STX] mmm nn e cc [ETX]

[STX] mmm nn OVER cc [ETX]

008

009

008

011

1234

ID•••1

ID•••4

ID•••3

ID•••2

ID No. 3 is

reading bar code

data ”1234“

1 2 ... 96 97 98 99 100 101 102 103 104 105 106 107 108 109

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Keyence BL-180 User Manual Page 101