GENERAL FEATURES
WHEN TO ACKNOWLEDGE
The SP400RF allows you to select the point at which the Base Station will acknowledge messages from the scanner. An "Acknowledge" is a re- sponse from the Base Station to the scanner with an ACK, WACK, NAK, or no response (see Communications Protocol at the start of this section for a definition of these terms). "When to Acknowledge" has three options:
Option ① - The Base Station acknowledges the receipt of a message from the scanner after the message is checked.
Option ➁ - The Base Station acknowledges receipt of a message from the scanner after the Base Station sends the last byte to the host Option ➂ - The Base Station acknowledges receipt of a message from the
scanner after CTS
RADIO AND INTERFACE LAYERS (SOFTWARE)
For the radio layer to validate a message, the transmission from the scanner to the Base Station is checked. (For example, CRC calculation, header format, correct number of bytes, etc.) For the interface layer to validate a message, the message from the radio layer is checked to ensure it is a valid label for a selected interface option.
SCANNER AUDIBLE RESPONSES
Once the scanner reads a barcode, it will produce a "Good Read" beep immediately. If the scanner does not receive a response from the Base Station within a programmed period of time after the label is read, the scanner will emit a "Bad Transmission" indication1 for the second beep. If the Base Station determines that the message is not a valid label for the interface, or the Base Station has been told via host commands or host handshaking to disable scanning, Base Station will send a NAK to the scanner. The scanner will then sound a "NAK from the Base" indication1 for the second beep. When any of the "When to Acknowledge" options are enabled, the Base Station will send an ACK to the scanner, causing it to sound an "ACK from the Base" indication1.
1Scanner beep indications are defined later in this section under the "When to Beep" Options heading.
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