Hardware Handshaking - Symbol DS3578 User Manual

8 - 10 DS3578 With FIPS Digital Scanner 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 the 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 the 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 still de-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 de-asserting 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 de-asserted for more than 50 ms
between characters, the transmission is aborted, the digital scanner sounds a transmission error, and the data is
discarded.
If this communications 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.
NOTE The DTR signal is jumpered (set) to the active state.
Scan one of the following bar codes to select a hardware handshaking option:
•
- Scan the bar code below if no hardware handshaking is desired.
None
•
Standard RTS/CTS
•
RTS/CTS Option 1
and ignores the state of CTS. The digital scanner de-asserts RTS when the transmission is complete.
•
RTS/CTS Option 2
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
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.
- Scan the bar code below to select standard RTS/CTS hardware handshaking.
- When RTS/CTS Option 1 is selected, the digital scanner asserts RTS before transmitting
- When Option 2 is selected, RTS is always high or low (user-programmed logic level).
- When Option 3 is selected, the digital scanner asserts RTS prior to any data