KEYENCE N-410 - Manual (Page 99)

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Details of Data Communication
This section describes the communication protocols and formats used for data communication.
Communication Protocol
The N-410 Series supports the following four handshaking protocols (data transfer procedures).
Both multi-drop Link Mode Data Communication (Auto-polling/manual polling), multi-head mode
data communication operate in the same way.
 No handshake
• The read data is sent to the host computer constantly. In other words, transmission is unregulated.
 PASS/RTRY protocol
• After read data is sent, the N-410 waits for a response (PASS or RTRY) from the host computer.
If a PASS (normal function) signal is sent to the N-410, one transmission has been completed and
the next can begin.
The N-410 does not send a response to a PASS signal.
• If the N-410 receives a RTRY (resend request) while waiting for a PASS signal, it resends the data and
resumes waiting for a PASS signal.
The N-410 does not reply to a RTRY signal if it has already received a PASS signal.
• Reading can occur while the device is waiting for a PASS signal. If this happens, the read data will
be stored in the N-410 send buffer.
If the send buffer capacity is exceeded, the N-410 will send an OVER message to the host computer all
data in the send buffer will be cleared.
In this case, the N-410 will halt and will reactivate upon receiving an OVCLR signal or having the
TEST switch pressed.
Refer to
"Send Buffer Capacity" (Page 4-9) for more information on send buffer capacity and
the OVER signal.
N-410
Read data
N-410
Read data
Response (PASS,RTRY)