RS-232 Interface 7 - 13

Software Handshaking

This paramete r offers con trol of the dat a transmission process in add ition to, or instead of, that offere d by hardware
handshaking. There are five options.
If software handshaking and hardware handshaking are both enabled, hardware handshaking takes precedence.

None

Select this option to tran sm it da ta immediate ly. No response is expected from the ho st.

ACK/NAK

If you select this option, afte r transmitting data, the digital scanner expects either an ACK or NAK response from
the host. When the scanner receives a NAK, it transmits the same dat a aga in and waits for either an ACK or NAK.
After three unsuccessful attempts to send data after the scanner rece ives NAKs, the scanner issues an error
indication and discards the data.
The digital scanner waits up to the programmable Host Serial Response T ime-out to receive an ACK or NAK. If the
digital scann er 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.

ENQ

If you select this option, the digital scanner waits for an ENQ character from the host before transmitting data. If it
does not receive an ENQ within th e Host Serial Response Time-out, the digital scanner issues an error indication
and discards the data. The host must transmit an ENQ character at lea st 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.

XON/XOFF

An XOFF character turns the digital scanner transmission off until the digital scanner receives an XON character.
There are two situations for XON/XOFF:
•
The digit al scanner r eceives an XOFF before it has data to send. When the digit al scanner has da t a to se nd,
it waits up to Host Serial Response Time-out for an XON character before transmission . If it does not receive
the XON within this time, the digital scanner issues an error indication and discards the data.
•
The digit al scanner r eceives an XOFF d uring a tra nsmis sion. Data transmission then stops af ter se nd ing the
current byte. When the digital scanner receives an XON character , it sends the r est of the data me ssage. The
digital scann er waits up to 30 seconds for the XON.