2019r0
Page 38 of 82
Mercury 2+ Operator Terminal User Manual
Transmission of messages in pointtopoint configuration is
immediate, i.e. at every key stroke, or promptly after a cardread.
The control codes and escape sequences described in this section
are available, with the exceptions noted.
Transmitted messages follow the format:
<STX> ADDR FUNC ID DATA DMY CSUM <ETX>
Point to Point
Transmission
Start Transmission (02
H
)
A two byte address field, as set up in Telemetry
Address with value 1 to 15. For multidrop mode see
page 40. This is always "01" in point to point mode.
Determines type of information being transmitted with
a single byte character. For messages transmitted from
the Mercury 2+ terminal this is always "D" (44
H
), and
"R" (52
H
) for messages received by the Mercury 2+
terminal.
Identifies source of data from a single byte:
"B" (42
H
) data from Wiegand Security Card swipe
"C" (43
H
) data from Proximity Card reading
"E" (45
H
) data from Digital Input read.
Other ID codes are available in Multidrop mode (see
page 40)
Information being sent from the identified source:
data from Security Card, encoded as hex ASCII, or
data for Digital Input reader as a single byte.
Single character, usually 00
H
but if this would result in
the following CSUM byte being a control character, the
DMY is set to 20
H
.
A single byte checksum character, which is the 7 bit
negated algebraic sum of all the characters in the string
from <STX> to DMY inclusive.
End Transmission character (03
H
) (see Table 4)
<STX>
ADDR
FUNC
ID
DATA
DMY
CSUM
<ETX>
Examples of messages are given in Appendix B.
