KEYENCE BL-180 - Manual (Page 55)

4.2 Details on Data Communication
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4.2 Details on Data Communication
4.2.1 Communication Protocols(Hardware handshaking)
The BL-180 supports the following four handshaking protocols.
No Handshaking
The BL-180 sends read data to the PC without using any handshaking protocol.
PASS/RTRY Handshaking
After sending the read data, the BL-180 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-180 then prepares for the next data transmission.
The RTRY command (request to re-send) indicates that the data was not trans-
mitted successfully. The command is a request to the BL-180 to re-send the data.
The BL-180 sends the same data again and then waits for the response.
After the BL-180 once receives PASS, the BL-180 sends back no data even if
RTRY is sent to the BL-180.
The BL-180 can continue to read while waiting for the PASS command. The data
is stored in the BL-180’s transmission buffer (For the capacity of the transmission
buffer, see page 48).
If the amount of stored data exceeds the capacity of the transmission buffer, the
BL-180 sends back
OVER to the PC, and clears all data
stored in the transmission buffer. For more information, see “Capacity of Trans-
mission Buffer” on page 48.
The BL-180 can receives other commands while waiting for the PASS command.
In this case, the BL-180 sends back an immediate response (e.g. OK).
When the SSET command (see “4.3.3” on page 52) is sent to the BL-180 while
the BL-180 is waiting for the PASS command, the BL-180 clears the data stored
in the transmission buffer, and enters the setting mode.
ACK/NAK Handshaking
The ACK/NAK handshaking uses ACK (06H) and NAK (15H) instead of PASS
and RTRY used in the PASS/RTRY handshaking, respectively. With these proto-
cols, the BL-180 sends back different characters, but performs the same opera-
tion.
Read data
(PASS , RTRY ) C
R
C
R
Read data
Response
Note