Hardware Handshaking - Motorola Symbol MS4404 Integration Manual

9 - 10 Symbol MS4404/MS4407 Integration Guide

Hardware Handshaking

The data interface consists of a serial 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, decoded data is transmitted as it becomes available. If Standard
RTS/CTS handshaking is selected, decoded data is transmitted according to the following sequence:
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The imager reads the CTS line for activity. If CTS is asserted, the imager 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 imager sounds a transmit error, and any decoded data is lost.
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When the CTS line is de-asserted, the imager 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 imager sounds a transmit error, and discards
the data.
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When data transmission is complete, the imager de-asserts RTS 10 msec after sending the last character.
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The host should respond by negating CTS. The imager 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 imager sounds a transmission error, and the data is
discarded.
If the above communication sequence fails, the imager issues an error indication. In this case, the data is lost and
must be recaptured.
If Hardware Handshaking and Software Handshaking are both enabled, Hardware Handshaking takes
precedence.
NOTE The DTR signal is jumpered to the active state.
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None: Capture the bar code below if no Hardware Handshaking is desired.
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Standard RTS/CTS: Capture 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 imager asserts RTS before transmitting and
ignores the state of CTS. The imager de-asserts RTS when the transmission is complete.
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RTS/CTS Option 2: When Option 2 is selected, RTS is always high or low (user-programmed logic level).
However, the imager waits for CTS to be asserted before transmitting data. If CTS is not asserted within Host
Serial Response Time-out (default), the imager issues an error indication and discards the data.
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RTS/CTS Option 3: When Option 3 is selected, the imager asserts RTS prior to any data transmission,
regardless of the state of CTS. The imager waits up to Host Serial Response Time-out (default) for CTS to be
asserted. If CTS is not asserted during this time, the imager issues an error indication and discards the data.
The imager de-asserts RTS when transmission is complete.