Motorola DS3478 - Manual (Page 111)

RS-232 Interface 7 - 13
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
Select this option to transmit data immediately. No response is expected from the host.
ACK/NAK
If you select this option, after 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 data again and waits for either an ACK or NAK.
After three unsuccessful attempts to send data after the scanner receives NAKs, the scanner issues an error
indication and discards the data.
The digital scanner waits up to the programmable Host Serial Response Time-out to receive an ACK or NAK. If the
digital scanner 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 the Host Serial Response Time-out, the digital 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 digital scanner transmission off until the digital scanner receives an XON character.
There are two situations for XON/XOFF:
• The digital scanner receives an XOFF before it has data to send. When the digital scanner has data to send,
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 digital scanner receives an XOFF during a transmission. Data transmission then stops after sending the
current byte. When the digital scanner receives an XON character, it sends the rest of the data message. The
digital scanner waits up to 30 seconds for the XON.