KEYENCE DV-90 - Manual (Page 182)

8-4 E DV-90-IM
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Data Communication Details
This section describes the communication protocol and communication format.
Communication Protocol
There are four types of communication protocol (data communication format) in the DV-90:
„ No Handshaking
The DV-90 sends the output data to the PC
with no handshaking.
„ PASS/R TRY protocol
➀The output data is sent to the PC from
the DV-90.
➁The DV-90 enters the waiting state
until a response (PASS: Normal end,
RTRY: Resend request) is received
from the PC.
➂When the PASS response is sent to the DV-90 from the PC, the first data communication ends,
and the next data is ready to be sent.
The DV-90 does not reply to the PASS response.
➃When the RTRY response is sent from the PC during the PASS waiting state, the DV-90 resends
the same data, and goes back into the PASS waiting state.
When the PASS or RTRY response is sent to the DV-90 when it is not in the PASS waiting state,
ERR00 is sent back.
➄In the DV-90, data from the code reader can be received during the PASS waiting time. The data
is saved in the send buffer.
(Communication format of PASS/RTRY)
For sending the PASS/RTRY commands, use one of the formats shown below.
In the following description, PASS is taken as an example, but RTRY must also be sent using the
same format.
PASS
PASS
PASS
PASS
Note
• When the amount of data exceeds the capacity (4000 bytes) of the send buffer, the
screen “Snd Buffer Over” is displayed. The operation stops after clearing the send buffer.
Press the key to recover.
• Commands other than PASS/RTRY cannot be accepted during the PASS waiting state.
(The unit shows no response.)
DV-90 PC
Output data
DV-90 PC
Output data
Response
ESC
CR
CR LF
ESC CR
ESC CR LF