Symbol Hotspot LS 2100, Product Reference Manual

Page: 86 / 350

6-13
RS-232 Interface
Hardware Handshaking
The data interface consists of an RS-232 port designed to operate either with or without the
hardware handshaking lines,
Request to Send ( RTS ) , and Clear to Send ( CTS ) .
If Standard RTS/CTS handshaking is not selected, scan data is transmitted as it becomes
available. If Standard RTS/CTS handshaking is selected, scan data is transmitted
according to the following sequence:
• The scanner reads the CTS line for activity. If CTS is asserted, the scanner waits
up to 2 seconds for the host to negate the CTS line. If, after 2 seconds (default),
the CTS line is still asserted, the scanner sounds a transmit error, and any scanned
data is lost.
• When the CTS line is negated, the scanner asserts the RTS line and waits up to 2
seconds for the host to assert CTS. When the host asserts CTS, data is
transmitted. If, after 2 seconds (default), the CTS line is not asserted, the scanner
sounds a transmit error, and discards the data.
• When data transmission is complete, the scanner negates RTS 10 msec after
sending the last character.
• The host should respond by negating CTS. The scanner checks for a negated CTS
upon the next transmission of data.
During the transmission of data, the CTS line should be asserted. If CTS is deasserted for
more than 50 ms between characters, the transmission is aborted, the scanner sounds a
transmission error, and the data is discarded.
If the above communications sequence fails, the scanner issues an error indication. In this
case, the data is lost and must be rescanned.
If Hardware Handshaking and Software Handshaking are both enabled, Hardware
Handshaking takes precedence.
Note: The DTR signal is jumpered to the active state.