Worth Data TriCoder t53, Руководство пользователя

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Appendix R
Polling and how it works
Polling is the operation where a TriCoder records data (either scanned or
entered on the keypad) and buffers it until the host computer asks the TriCoder
to transmit the data. The request for the data from the host is called a "poll".
The TriCoder then transmits its data (along with its ID character to identify
which TriCoder the data came from) to the host and goes on to record another
piece of information and wait for it's next poll. Polling is not considered a
"portable" operation and requires that you use the 5 volt power adapter with the
TriCoder. Polling works only with serial interface readers.
Polling with the TriCoder
Here is what polling looks like on the TriCoder:
The TriCoder reads a code, beeps once, and displays the data on the 1st line
and
WAITING ON POLL on the 2nd line. The TriCoder stores the data in
its buffer, waiting for the host to ask for it. For the purposes of this
explanation, let's suppose that the person using a TriCoder with the ID
character “
a” just read the bar code 123456 and the person using TriCoder
“ b ” is on a lunch break. The software running on the host computer
transmits each of your TriCoders' ID characters one by one over the serial
port. As each TriCoder's ID character is transmitted, the TriCoder with the
matching ID character responds with one of the following:
1. If the TriCoder has no data in its buffer to transmit, it sends
back its ID CHARACTER only .
2. If the TriCoder has data to transmit, it sends back its ID
CHARACTER followed by the data .
When the host program transmits an “ a ”, the TriCoder with the ID character
of “ a ” responds with “ a123456 ”. The TriCoder screen goes blank and is
ready for more data. When the host computer sends out a “ b ” polling
character, TriCoder “ b ” responds with a “ b ” only (its operator is at lunch
and has recorded no data). TriCoder “ b ” then clears its screen and is ready
for data. The host software reads the transmitted data from the serial port
and processes it according to your needs.
The software can tell which TriCoder transmitted which piece of data by the
ID character preceding the data. If you don’t care what belongs to what, the
ID can be discarded. The computer and TriCoders poll and respond very
quickly. People using the TriCoders are seldom conscious of any delay due
to polling. The TriCoder Utilities diskette contains a basic program that
polls and differentiates between data from three TriCoders that have been
assigned ID characters of “
a ”,” b ”, and ” c ”.
Polling with “Host Response Accepted”
Host Response Accepted is one of the protocols used with Polling. Host
Response Accepted allows the TriCoder to act on data received from the