Symbol DS 3408, Руководство по продукции

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7 - 12 Symbol DS3408 Product Reference Guide
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 digital scanner reads the CTS line for activity. If CTS is asserted, the digital scanner waits up to Host
Serial Response Time-out for the host to de-assert the CTS line. If, after Host Serial Response Time-out
(default), the CTS line is still asserted, the digital scanner sounds a transmit error, and any scanned data is
lost.
•
When the CTS line is de-asserted, the digital scanner asserts the RTS line and waits up to Host Serial
Response Time-out for the host to assert CTS. When the host asserts CTS, data is transmitted. If, after Host
Serial Response Time-out (default), the CTS line is not asserted, the digital scanner sounds a transmit error,
and discards the data.
•
When data transmission is complete, the digital scanner de-asserts RTS 10 msec after sending the last
character.
•
The host should respond by negating CTS. The digital scanner checks for a de-asserted 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 digital scanner sounds a transmission error, and the data is
discarded.
If the above communication sequence fails, the digital 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.
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None : Scan the bar code below if no Hardware Handshaking is desired.
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Standard RTS/CTS : Scan the bar code below to select Standard RTS/CTS Hardware Handshaking.
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RTS/CTS Option 1 : When RTS/CTS Option 1 is selected, the digital scanner asserts RTS before
transmitting and ignores the state of CTS. The digital scanner de-asserts RTS when the transmission is
complete.
•
RTS/CTS Option 2 : When Option 2 is selected, RTS is always high or low (user-programmed logic level).
However, the digital scanner waits for CTS to be asserted before transmitting data. If CTS is not asserted
within Host Serial Response Time-out (default), the digital scanner issues an error indication and discards
the data.
•
RTS/CTS Option 3 : When Option 3 is selected, the digital scanner asserts RTS prior to any data
transmission, regardless of the state of CTS. The digital scanner waits up to Host Serial Response Time-out
(default) for CTS to be asserted. If CTS is not asserted during this time, the digital scanner issues an error
indication and discards the data. The digital scanner de-asserts RTS when transmission is complete.
NOTE The DTR signal is jumpered to the active state.