KEYENCE BL-700 Series User Manual
Page 100
Chapter 5 Serial Communication
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5
■ ACK/NAK Handshaking
The ACK/NAK handshaking uses
and RTRY used in the PASS/RTRY handshaking, respectively. With these proto-
cols, the BL-700 sends back different characters, but performs the same operation.
■ RTS/CTS Handshaking
•
When the PC’s RTS (BL-700’s CTS) signal turns off, the BL-700 becomes
ready for data transmission. When the PC’s RTS signal turns on, the BL-700
starts data transmission.
•
When the PC’s RTS signal is off, the BL-700 can still read. In this case, data is
stored in the BL-700’s transmission buffer (see below).
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 when the RTS of
the computer turns ON.
Note 1: The RTS/CTS handshaking cannot be used for RS-422A communication.
Note 2: The RTS/CTS protocol can be used together with other handshaking
protocols.
Note 3: When the PC’s RTS signal is off, the BL-700 does not sends back a
response to the PC.
Capacity of transmission buffer
The BL-700’ s transmission buffer can store 400 bytes (400 characters).
The number of characters stored in the transmission buffer for each data packet is
the number of characters in the data (including additional data such as the number
of decoding match count) plus an additional five characters indicating the data’s
attributes.
When multi label reading mode 2 or 3 is used, these five attribute characters are
added to each data packet.
Example 1
When the number of bar code digits is 10 (with no additional data)
400 ÷ (10 + 5) = 26
The transmission buffer can store 26 pieces of data.
Example 2
When the number of bar code digits is 20 (with no additional data)
400 ÷ (20 + 5) = 16
The transmission buffer can store 16 pieces of data.