Enq; Ack/Nak With Enq; Xon/Xoff - Motorola Symbol DS3578 Product Reference Manual

Software Handshaking (continued)

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
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 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 transmission. If the XON is not received within
this time, the scanner issues an error indication 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.
ENQ
ACK/NAK with ENQ
XON/XOFF
RS-232 Interface 7 - 15