Symbol Technologies DS 3408 - Manual (Page 96)

DS 3408 Product Reference Guide 7-14
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.
The DTR signal is jumpered to the active state.
• None: Scan the bar code below if no Hardware Handshaking is desired.
• Standard RTS/CTS: Scan the bar code below to select Standard RTS/CTS Hardware Handshaking.
• 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