Symbol P 300STD Product Reference Manual page 141

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 scanner issues an
error beep 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
beep 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 2 seconds, the scanner
issues an error indication and discards the data. The host must transmit an ENQ
character at least every 2 seconds to prevent transmission errors.
ACK/NAK with ENQ
!
This combines the two previous options.
XON/XOFF
!
An XOFF character turns the scanner transmission off until the scanner receives an
XON character. There are two situations for XON/XOFF:
ACK/NAK
ENQ
ACK/NAK with ENQ
Programming the Scanner
2-105