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RS-232 Host Interface 6-21

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 scanner reads the CTS line for activity. If CTS is asserted, the scanner waits up to 2 seconds for the host to negate the

CTS line. If, after 2 seconds (default), the CTS line is still asserted, the scanner sounds a transmit error, and any scanned

data is lost.

• When the CTS line is negated, the scanner asserts the RTS line and waits up to 2 seconds for the host to assert CTS. When

the host asserts CTS, data is transmitted. If, after 2 seconds (default), the CTS line is not asserted, the scanner sounds a

transmit error, and discards the data.

• When data transmission is complete, the scanner negates RTS 10 msec after sending the last character.

• The host should respond by negating CTS. The scanner checks for a negated 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 scanner sounds a transmission error, and the data is discarded.

If the above communications sequence fails, the 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.

*None

Note

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Motorola SYMBOL LS7708 Specifiche Pagina 127