KEYENCE BL-N90 Series - Manual (Page 52)

3-4 Settings for Each Communication Interface
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ACK/NAK
The reader sends data between the host by using the following procedure.
1 Read data is sent to the host from BL-N9R.
BL-N9R waits for a response from the host (ACK [06h]: Completed without errors, NAK
[15h]: Request resend). While waiting for ACK [06h], the next barcode cannot be read.
2 The response is sent from the host to BL-N9R.
• When the ACK [06h] response is sent, the first communication is completed.
BL-N9R can send the following read data (it does not respond with ACK [06h]).
• When the NAK [15h] response is sent, BL-N9R resends the same data and waits for the
ACK [06h] response.