FRICK
®
QUANTUM™ LX AcuAir
®
CONTROL PANEL S90-510 CS (MAR 07)
COMMUNICATIONS SETUP Page 33
Query (Read) Example:
To demonstrate how an address within the
Quantum™ may be read, the following test can
be performed using Windows HyperTerminal:
As an example, a MODBUS
®
command will be
created, and sent to obtain the actual Outside Air
Temperature value of Air Handling Unit #1. Using
the address tables found later in this manual,
locate the address for Unit 1 Outside Air
Temperature Analog Input. In this case, it would
be Frick
Address 2000 (decimal). Since this is
the only address we are interested in obtaining
the value of, send the following message:
Look at this message on a more basic level, to
understand how the address that we are
requesting is arrived at.
The first part of the message will be a Colon ( : ).
This represents a “heads up” alert that data is
coming “down the line”.
Any time that a message is sent, all of the Quantum™
panels that are on the MODBUS
®
network will become
active, communications wise, once the Colon appears.
Next, all panels will look at the first byte following the
Colon ( : ). If this byte equals the Panel ID # of the
particular Quantum™ being queried, it will immediately
finish reading the remainder of the message. If the byte
does not equal its ID #, the message will be ignored.
In this particular example, we are strictly looking to request
to view a data value, so we will be performing a read
function (03):
Address 2000 decimal equals 7D00 hex. Looking at our
example, we see that we need a H.O. (High Order)
address and a L.O. (Low Order) address. Since all data
sent and received is in ASCII Hex Byte format, we need to
look at 00 Hex as the Low Order portion of the address.
The High Order portion is 7D. Now our decimal 2000 is
formatted as 7D00 Hex.
Since we are only looking for this one address, and no
other, we can say that we are only looking for one Data
Address. Our Data Address part of the data packet is also
looking for a High and a Low Order value. Fortunately, the
number one (1) is the same in decimal as it is in Hex,
therefore, the Low Order Address is 01 (hex). The High
Order Address is 00 (hex), so our decimal 1 is formatted
as 0001 (hex).
}
Where:
Message Start
Quantum™ ID #
Read Function
H.O. address (hex)
L.O. address (hex)
H.O. # of Data Registers
L.O. # of Data Registers
Error Correction Code
Carriage Return – Line Feed
: 01 03 7D 00 00 01 7E CRLF
}
Where:
Message Start
Quantum™ ID #
Read Function
H.O. address (hex)
L.O. address (hex)
H.O. # of Data Registers
L.O. # of Data Registers
Error Correction Code
Carriage Return – Line Feed
: 01 03 7D 00 00 01 7E CRLF
}
Where:
Message Start
Quantum™ ID #
Read Function
H.O. address (hex)
L.O. address (hex)
H.O. # of Data Registers
L.O. # of Data Registers
Error Correction Code
Carriage Return – Line Feed
: 01 03 7D 00 00 01 7E CRLF
}
Where:
Message Start
Quantum™ ID #
Read Function
H.O. address (hex)
L.O. address (hex)
H.O. # of Data Registers
L.O. # of Data Registers
Error Correction Code
Carriage Return – Line Feed
: 01 03 7D 00 00 01 7E CRLF
Where:
Message Start
Quantum™ ID #
Read Function
H.O. address (hex)
L.O. address (hex)
H.O. # of Data Registers
L.O. # of Data Registers
Error Correction Code
Carriage Return – Line Feed
: 01 03 7D 00 00 01 7E CRLF
}