Symbol LS 4071, Product Reference Manual

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LS 4071 Product Reference Guide
RS-232C Parameters
Hardware Handshaking
The data interface consists of an RS-232C port. The port has been designed to
operate either with or without the hardware handshaking lines, RTS, Request to
Send, and CTS, Clear to Send.
If Standard RTS/CTS handshaking is selected, scan data is transmitted
according to the following sequence:
•
The base reads the CTS line for activity. If CTS is asserted, the base waits
up to two seconds for the host to negate the CTS line. If, after two seconds
(default), the CTS line is still asserted, the base sounds a transmit error
and any scanned data is lost.
•
When the CTS line is negated, the base asserts the RTS line and waits up
to two seconds for the host to assert CTS. When the host asserts CTS, data
is transmitted. If, after two seconds (default), the CTS line is not asserted,
the base sounds a transmit error and discards the data.
•
When data transmission is complete, the base negates RTS 10 msec after
sending the last character.
•
The host should respond by negating CTS. The base 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 base sounds a transmission error, and the data is discarded.
If the above communications sequence fails, the base 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 will take precedence.
Note:
The DTR signal is jumpered active.