KEYENCE N-400 User Manual

Page 74

Chapter 4 Multi-Drop Link Mode Control Procedure

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The “PASS” and “RTRY” commands can be received in either of the following
formats:

PASS [CR], or [STX] PASS [ETX]

[ESC] can be added to the head of the command, or [LF] can be added to the
end of the command.

Note 1: Even when the N-400 is waiting for the “PASS” command, it can still
receive any type of command. In this case, the N-400 immediately sends back a
response (e.g. “OK”) to the host computer.

Note 2: If the “SSET” command (

➮

see p. 73) is sent to the N-400 while it is waiting

for the “PASS” command, the N-400 clears the data stored in the transmission
buffer and goes into SETUP mode.

ACK/NAK protocol

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The ACK/NAK protocol uses [ACK] (06H) instead of “PASS”, and [NAK] (15H)
instead of “RTRY” described in the above protocol. The operation is the same
as the above protocol; only the response codes are different.

RTS/CTS control

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When the RTS signal is turned OFF during RS-232C communication, the N-400
becomes ready for data transmission. When the RTS signal is turned ON, the
N-400 starts sending data. This cannot stop/start the data transmission once
data is being sent. It is effective for controling the transmission of a set of data.

•

Even when the RTS signal is OFF, the BL series can read bar code data. In this
case, the read data is stored in the transmission buffer of the N-400. (

➮

For the

buffer capacity, see p. 63.) If the amount of read data exceeds the buffer capac-
ity, the N-400 clears all data stored in the transmission buffer. In this case, the
N-400 stops its operation. The N-400’s operation restarts when the RTS signal
is turned ON, or when the N-400 sends back the “OVER” code to the host
computer. (

➮

See p. 63.)

Note 1: The RTS/CTS control can be used together with other handshaking
protocols.

Note 2: When the RTS signal is OFF, the N-400 does not send back a response
(e.g. “OK) to the host computer.