Motorola Symbol PL4507, Руководство по интеграции

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Serial Interface 7 - 11
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, scan data transmits as it becomes available. Select Standard
RTS/CTS handshaking to transmit scan data according to the following sequence:
•
The decoder reads the CTS line for activity. If CTS is asserted, the decoder waits up to the Host Serial
Response Time-out for the host to de-assert the CTS line. If, after the Host Serial Response Time-out
(default) the CTS line is still asserted, the decoder sounds a transmit error and discards any scanned data.
•
When the CTS line is de-asserted, the decoder asserts the RTS line and waits up to the Host Serial
Response Time-out for the host to assert CTS. When the host asserts CTS, data transmits. If, after the Host
Serial Response Time-out (default) the CTS line is not asserted, the decoder sounds a transmit error and
discards the data.
•
When data transmission completes, the decoder de-asserts RTS 10 msec after sending the last character.
•
The host responds by negating CTS. The decoder checks for a de-asserted CTS upon the next transmission
of data.
During data transmission, the CTS line should be asserted. If CTS is deasserted for more than 50 ms between
characters, the decoder aborts transmission, sounds a transmission error, and discards the data.
If the above communication sequence fails, the decoder 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.
•
None : Scan this bar code to disable hardware handshaking.
•
Standard RTS/CTS : Scan this bar code to select Standard RTS/CTS Hardware Handshaking.
•
RTS/CTS Option 1 : The decoder asserts RTS before transmitting and ignores the state of CTS. The decoder
de-asserts RTS when transmission completes.
•
RTS/CTS Option 2 : RTS is always high or low (user-programmed logic level). However, the decoder waits
for CTS to be asserted before transmitting data. If CTS is not asserted within Host Serial Response Time-out
(default), the decoder issues an error indication and discards the data.
•
RTS/CTS Option 3 : The decoder asserts RTS prior to any data transmission, regardless of the state of CTS.
The decoder waits up to Host Serial Response Time-out (default) for CTS to be asserted. If CTS is not
asserted during this time, the decoder issues an error indication and discards the data. The decoder
de-asserts RTS when transmission completes.
NOTE The DTR signal is jumpered to the active state.