Pavone Systems DAT 100, Техническое руководство

Страница: 28 / 38

Page 26
SERIAL COMMUNICATION PROTOCOLS
The COM1 RS232 serial port is always available, while the COM2 RS485 serial port is only available
in the instrument:
DAT 100 /RS485.
On the COM2 RS485 the serial transmission protocols and the MODBUS RTU protocol are handled.
CONTINUOUS, AUTOMATIC AND MANUAL TRANSMISSION PROTOCOL
These protocols have been programmed into their programming menu.
The string transmitted is as follows:
STX <state> <weight> ETX <chksum> EOT
Where
STX (start of text) = 0x02h
ETX (end of text) = 0x03h
EOT (end of transmission) = 0x04.
<state> = character encoded as per the following table (bit = 1 if condition TRUE)
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
0 0 1 1
Tare
entered
Zero
band
Stable
weight
Zero
center
<weight> = field consisting of 8 ASCII characters with the weight value justified on the right. (without
leading zeros, with possible decimal point and negative sign).
The weight value transmitted can be the net weight, the gross weight or the peak value based on the
selection of the transmitted data (MODE parameter) in the setting menu of the serial communication
ports (see relevant paragraph).
Under conditions of overload, the weight field assumes the value: “^^^^^^^^”.
Under conditions of underload (negative weight greater than 99999), the weight field assumes the
value: “_ _ _ _ _ _ _ _”.
In reading error conditions, the weight field assumes the value: “ O-L ”.
<csum> = checksum of the string data. It is calculated by performing the exclusive OR (XOR) of all
characters from STX (or from <ind>) to ETX excluded the latter; the result of the XOR is decomposed
into 2 characters by considering separately the upper 4 bits (first character) and lower 4 bits (second
character); the 2 characters obtained are then ASCII encoded (example: XOR = 5Dh; <csum> = “5Dh”
namely 35h and 44h).
In the case of continuous communication protocol, the given string is transmitted at a frequency of 10
Hz, regardless of the weight filter selected.
In the case of automatic and manual communication protocols, between 2 consecutive weight transmis-
sions, they must undergo a corresponding change to the value set in DELTA parameter, in the setup
menu of weighing parameters (see relevant paragraph).