2 details on data communication – KEYENCE BL-700 Series User Manual
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Chapter 5 Serial Communication
5
5.2
Details on Data Communication
Communication protocols (Hardware handshaking)
The BL-700 supports the following four handshaking protocols.
■ No Handshaking
•
The BL-700 sends read data to the PC without using any handshaking protocol.
■ PASS/RTRY Handshaking
•
After sending the read data, the BL-700 waits for a response from the PC. The
response is either a PASS command or a RTRY command.
The PASS command (quit) indicates that the PC has successfully received one
data packet. The BL-700 then prepares for the next data transmission.
•
The RTRY command (request to re-send) indicates that the data was not
transmitted successfully. The command is a request to the BL-700 to re-send
the data. The BL-700 sends the same data again and then waits for the re-
sponse.
After the BL-700 once receives PASS, the BL-700 sends back no data even if
RTRY is sent to the BL-700.
•
The BL-700 can continue to read while waiting for the PASS command. The
data is stored in the BL-700’s transmission buffer.
➮ For the capacity of the transmission buffer, see P.86.
If the amount of stored data exceeds the capacity of the transmission buffer, the
BL-700 sends back [Header]OVER[Delimiter] to the PC, and clears all data
stored in the transmission buffer.
The BL-700 stops operation while clearing data. It recovers by sending PASS to
[Header]OVER[Delimiter].
•
PASS and RTRY can be received in either communication format: PASS
or
the end of the format.
Note 1: The BL-700 can receives other commands while waiting for the PASS
command. In this case, the BL-700 sends back an immediate response (e.g. OK).
Note 2: When the SSET command (
➮ see P.92) is sent to the BL-700 while the
BL-700 is waiting for the PASS command, the BL-700 clears the data stored in the
transmission buffer, and enters the setting mode.
Read data
LASER O
N
STB
OK/NG
TIMIN
G
TEST
BL-700
(PASS, RTRY)
Read data
Response
LASER ON
STB
OK/NG
TIMING
TEST
BL-700