2-13
Programming
RS-232C Options (Continued)
Software Handshaking
This parameter controls the data transmission process. It may be used instead
of, but not in conjunction with, hardware handshaking.
The scanner provides five software handshaking options, listed below. Refer to
the flow chart on the following page.
1. None
2. ACK/NAK Only
The ACK/NAK option checks the result of a transmission. The scanner
expects one of the following host responses after a data transmission:
<ACK> - Acknowledges a valid and successful transmission.
<NAK> - Indicates a problem with the transmission.
Whenever a <NAK> is received, the unit retransmits the same data and
awaits an ACK/NAK response. After three unsuccessful attempts to
transmit the same data, the scanner aborts any further communication
attempts on that message. Transmission error is indicated by the unit
sounding 4 short beeps.
3. ENQ ONLY
The ENQ option needs the host to request data before it is transmitted to
the host. This ensures that data transmission occurs only when the host is
ready to rec eive.
When you select the ENQ option, the scanner waits for an ENQ, Enquire
character, from the host before it transmits data; otherwise the unit
transmits data without waiting for an ENQ character from the host. With
ENQ enabled, the scanner must receive an ENQ from the host within a 2
second period after the last activity or 4 short beeps are sounded to indicate
a transmission error; the unit is now ready to scan again.
4. ACK/NAK with ENQ
This combines both handshaking options.