RS-232 Interface 9 - 11
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 hardware handshaking and software handshaking are both enabled, hardware handshaking takes precedence.
Options:
•
None - This disables hardware handshaking and transmits scan data as it becomes available.
•
Standard RTS/CTS - This sets standard RTS/CTS hardware handshaking and transmits scanned data
according to the following sequence:
a. The scanner reads the CTS line for activity:
• If the CTS line is de-asserted, the scanner asserts the RTS line and waits up to Host Serial Response
Timeout on page 9-15 for the host to assert CTS, and then transmits data when asserted. If, after the
timeout, the CTS line is not asserted, the scanner sounds a transmit error and discards the data.
• If CTS is asserted, the scanner waits up to Host Serial Response Timeout for the host to de-assert
CTS. If after this timeout the CTS line is still asserted, the scanner sounds a transmit error and discards
the scanned data.
b. The scanner de-asserts RTS after sending the last character of data.
c. The host negates CTS. The scanner checks for a de-asserted CTS upon the next data transmission.
During data transmission, if CTS is deasserted for more than 50 ms between characters, the scanner sounds
a transmit error and discards the data. The data must be re-scanned.
•
RTS/CTS Option 1 - The scanner asserts RTS before transmitting and ignores the state of CTS. The
scanner de-asserts RTS when transmission completes.
•
RTS/CTS Option 2 - RTS is always high or low (user-programmed logic level). However, the scanner waits
for the host to assert CTS before transmitting data. If CTS is not asserted within the Host Serial Response
Timeout, the scanner sounds a transmit error and discards the data. During data transmission, if CTS is
deasserted for more than 50 ms between characters, the scanner sounds a transmit error and discards the
data.
•
RTS/CTS Option 3 - This transmits scanned data according to the following sequence:
a. The scanner asserts RTS before data transmission, regardless of the state of CTS.
b. The scanner waits up to the Host Serial Response Timeout for the host to assert CTS, and then transmits
data when asserted. If, after the timeout, the CTS line is not asserted, the scanner sounds a transmit error
and discards the data.
c. The scanner de-asserts RTS after sending the last character of data.
d. The host negates CTS. The scanner checks for a de-asserted CTS upon the next data transmission.
During data transmission, if CTS is deasserted for more than 50 ms between characters, the scanner sounds
a transmit error and discards the data. The data must be re-scanned.
NOTE The DTR signal is jumpered to the active state.
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