HHD II
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4.1.2
ACK/NACK Protocol
This parameter sets a transmission protocol in which the Host responds to the reader
after every code transmitted. The Host sends an ACK character (06 HEX) in the case
of good reception or the NACK character (15 HEX) requesting re-transmission, in the
case of bad reception.
If the reader does not receive an ACK or NACK, transmission is ended after the RX
Timeout (see par. 4.1.4).
Selection of the ACK/NACK protocol automatically disables FIFO buffering see par.
4.1.3.
4.1.3
FIFO
This parameter determines whether data (barcodes) are buffered on a First In First
Out basis allowing faster data collection in certain cases for example when using
slow baud rates and/or hardware handshaking.
If the FIFO buffering is enabled, codes are collected and sent out on the serial line in
the order of acquisition. Several hundred characters can be collected (buffer full),
after which the reader signals an error and discards any further codes until the
transmission is restored.
If the FIFO buffering is disabled, each code must be transmitted before another one
can be read.
4.1.4
RX Timeout
When the RS232 interface is selected, the Host can be used to configure the device
by sending it command strings (see appendix A).
This parameter can be used to automatically end data reception from the Host after
the specified period of time.
If no character is received from the Host, after the timeout expires, any incomplete
string (any string not terminated by <CR>) is flushed from the device buffer.
Summary of Contents for Hand-Held Devices II
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