6 - 12 Symbol LS4208 Product Reference Guide

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: When this option is selected, data is transmitted immediately. No response is expected from host.
•
ACK/NAK: When this option is selected, afte r 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 o r NAK. After three unsuccessful attempt s to send dat a when NAKs are receive d, the scanner
issues an error indication and discards the data.
The scanner waits up to the programmab le Host Serial Response Ti me-out to receive an ACK or NAK. If the
scanner does not get a respon se in this time, it issues an error indication and di scards the data . There are no
retries when a time-out occurs.
•
ENQ: When this option is selected, the scanner wait s 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 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 scanner transmission off until the scanner receives an XON
character. There are two situations for XON/XOFF:
•XOFF is received b efor e the scanner ha s d ata to se nd. When the scanne r ha s data to send, it waits up to
Host Serial Response Time-out for an XON character before transmission. If the XON is not received
within this time, the scanner issues an error indication and discard s the data.
•XOFF is received during a transmission. Data tran smission then stops after sending the current byte.
When the scanner receives an XON ch aracter, it sends the rest of the dat a message. The scanner waits
up to 30 seconds for the XON.