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RS-232 Interface 8 - 13
Hardware Handshaking (continued)
Software Handshaking
This parameter offers control of the data transmission process in addition to, or instead of, that offered by
hardware handshaking. There are five options.
If Software Handshaking and Hardware Handshaking are both enabled, Hardware Handshaking takes
precedence.
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None: When this option is selected, data is transmitted immediately. No response is expected from host.
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ACK/NAK: When this option is selected, after transmitting data, the digital imager scanner expects either
an ACK or NAK response from the host. When a NAK is received, the digital imager scanner transmits
the same data again and waits for either an ACK or NAK. After three unsuccessful attempts to send data
when NAKs are received, the digital imager scanner issues an error indication and discards the data.
The digital imager scanner waits up to the programmable Host Serial Response Time-out to receive an
ACK or NAK. If the digital imager scanner does not get a response in this time, it issues an error
indication and discards the data. There are no retries when a time-out occurs.
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ENQ: When this option is selected, the digital imager scanner waits for an ENQ character from the host
before transmitting data. If an ENQ is not received within the Host Serial Response Time-out, the digital
imager scanner issues an error indication and discards the data. The host must transmit an ENQ
character at least every Host Serial Response Time-out to prevent transmission errors.
•
ACK/NAK with ENQ: This combines the two previous options. For re-transmissions of data, due to a
NAK from the host, an additional ENQ is not required.
RTS/CTS Option 2
RTS/CTS Option 3