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RS-232 Host Parameters
Product Reference Guide 43
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.
• None: When this option is selected, data is transmitted immediately. No response is
expected from host.
• ACK/NAK: When this option is selected, after transmitting data, the scanner expects
either an ACK or NAK response from the host. When a NAK is received, the scanner
transmits the same data again and waits for either an ACK or NAK. After three unsuccess-
ful attempts to send data when NAKs are received, the scanner issues an error indication
and discards the data.
The scanner waits up to the programmable Host Serial Response Time-out to receive an
ACK or NAK. If the scanner does not get a response in this time, it issues an error indica-
tion and discards the data. There are no retries when a time-out occurs.
• ENQ: When this option is selected, the 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 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 trans-
mission 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.
• XON/XOFF: An XOFF character turns the scanner transmission off until the scanner
receives an XON character. There are two situations for XON/XOFF:
- XOFF is received before the scanner has data to send. When the scanner has data to
send, it waits up to Host Serial Response Time-out for an XON character before trans-
mission. If the XON is not received within this time, the scanner issues an error indica-
tion and discards the data.
- XOFF is received during a transmission. Data transmission then stops after sending the
current byte. When the scanner receives an XON character, it sends the rest of the data
message. The scanner waits up to 30 seconds for the XON.