Q-2
host computer. The host can send data to the TriCoder to control the beeper,
display data on the TriCoder screen or broadcast a voice message. If you
are using the Host Response Accepted Protocol setup option, observe the
following rules:
1. To prevent conflict between ID characters and data characters,
the displayable data characters must be limited to ASCII 32-
95. In other words, no lower case letters are permissible.
2. ID characters must be ASCII 96-127.
3. A displayable prompt must be terminated by a CR unless you
are sending TriCoder beeper control characters BEL, DC2, or
nnDC4 (where nn is the voice message number). The beeper
control characters are the termination for the prompt instead of
a CR. A displayable prompt can also be a single character of
CR, BEL, DC2, or nnDC4.
4. In order to prevent the loss of a message from the host, the
TriCoder locks out scanning or keyboard data entry until it
receives a valid prompt from the host. The Tricoder displays
the following message until it receives the prompt:
WAITING ON PMPT
If you want to change anything (including scanning the Setup
Menu) without receiving the expected prompt from the host,
you must first press the CLEAR key on the TriCoder keypad.
Polling with ACK/NAK
The Polled with ACK/NAK option allows for greater data accuracy by
using ACK/NAK protocol while polling. The TriCoder appends two
checksum characters upon transmission of its data. The host computer
receives this data, calculates the checksum then compares it to the
checksums transmitted by the TriCoder. If they are the same, the host sends
an ACK (ASCII 6). If they are different, the host sends a NAK (ASCII 21).
If the TriCoder receives 10 NAK's in a row, it suspends operation.
Sometimes it is desirable to know whether the TriCoder is "waiting on a
poll" or "waiting on an ACK/NAK". A setup parameter is available that
displays either the message WAITING ON POLL or WAIT ON
ACK/NAK, depending on which condition is present. This feature is
activated through the bar coded TriCoder Setup Menu by scanning
Terminator Character, then A. To get rid of the extra messages, scan B.
For more information on Polling with ACK/NAK and a sample program
(BASIC), see the TriCoder Utilities disk.
