When not using hardware handshaking, space messages
sufficiently apart. The host must not communicate with the scanner
if the scanner is transmitting.
When using hardware handshaking, frame each message properly
with handshaking signals. Do not try to send two commands within
the same handshaking frame.
There is a permanent/temporary bit in the PARAM_SEND message.
Removing power from the scanner discards temporary changes. Permanent
changes are written to non-volatile memory. Frequent changes shorten
the life of the non-volatile memory.
