x1xx
Button 2 pressed,
bit 5
xx1x
Button 3 pressed,
bit 6
Two or more buttons may be
pressed simultaneously, e.g.
1010 = 1, 3 pressed.
xxx1
Button 4 pressed,
bit 7
The Jamming Bits
There are two standards for jamming decision that are implemented
in the system: European standard and American (USA) standard. The
two differ slightly.
The common part of those standards is:
1.
For every second, a
jamming state
is detected if during 18% of a
second the disturbances are larger than a predefined threshold.
2. Jamming event
is declared if the jamming state persists for 30 or
more seconds of the minute.
The difference between the USA and European standards are as
follows:
•
USA standard requests continuous 30 or more seconds of
jamming state.
•
European standard requests any 30 or more seconds of
jamming state during one minute.
Clearly, not every jamming event defined as European standard is
considered a jamming event according to USA standard.
CodeSecure Implementation
CodeSecure implements the KELOQ code hopping technology to
make each transmission by an encoder unique. The encoder
transmissions are comprised of two parts. The first part changes each
time the encoder is activated and is called the "hopping code". The
second part is the serial number of the encoder (ID), recognizable to
a decoder.
The hopping code
contains function information, a discrimination
value and a synchronization counter. An encryption algorithm
encrypts this information before being transmitted. The encryption
algorithm uses a 64-bit encryption key. If one bit in the data that is
encrypted changes, the result is that an average of half of the bits in
the output will change. As a result, the hopping code changes
dramatically for each transmission and cannot be predicted.
The transmitted word contains a 16-bit
synchronization counter
.
The counter is incremented every time the encoder is activated.
The synchronization information is used at the decoder to determine
whether a transmission is valid, or a repetition of a previous
transmission is being sent. When a following transmission is received
from the same transmitter it is possible to verify whether the
transmission is valid. Previous codes are rejected to safeguard "code
grabbers". The range of the synchronization counter is 65,536. Each
transmission, for example, a button press, generates a new
synchronization number, one out of the 65,356.
Implementation Guidelines
Storing serial numbers
- The synchronization counter value is
stored in EEPROM of the control panel every time a valid
transmission is received from a particular encoder.
It is highly
recommended to keep two copies of the synchronization counter
in two different EEPROM locations
. This is because that in the
event of a power failure during an EEPROM write, a corrupted
counter value would be read when the control panel is later powered
up, resulting in encoder transmissions erroneously being discarded
as invalid.
The encoder’s serial number is transmitted every time a button is
pressed. The serial number is transmitted unencrypted as part of the
transmission. A serial number is used at the Receiver Module to check
message correction after message decryption, and at the control panel
to verify whether transmitter is valid.
Serial numbers of every valid
transmitter must be stored in EEPROM of the control panel
.
Algorithm of synchronization counter control
Conditions must be established where the transmitter is pressed while
out of valid range of the RF Receiver. Allowing two “synchronization
windows” achieves this:
•
The open window
•
The resynchronization window
The
open window
is a reception of a transmission where the
synchronization counter is 1 to 16 higher than the previous counter
value received. The reception of such a signal will result in an
immediate counter update by the control panel program and the
appropriate outputs being activated.
If the transmitter is pressed more than 16 times out of range of the
receiver, resynchronization needs to be performed. The
resynchronization window
is half of the total counter range, 32K
numbers. During resynchronization, the control panel program waits
for two consecutive transmissions from the encoder before
resynchronization occurs and the resynchronized counters are
updated in the EEPROM of the control panel. When the control panel
receives a transmission with a synchronization counter value more
than 16 above the stored counter value and less than 32,768 counts
above the stored value, the control panel temporarily stores the value
of the synchronization counter received. If the next transmission
received has a synchronization counter value of one above the
previous sent, the control panel resynchronizes on the last
transmission received and activates the appropriate outputs.
If any of the above tests fail, the transmission received is discarded.
5. OPERATION
5.1 Viewing all Detector IDs
Note: Use a MCR-300/UART unit whose receiving frequency is
identical to the frequency of the detectors.
The following steps are performed for checking detector IDs within the
system.
1.
Insert the CD-ROM into the CD-ROM drive.
2.
Copy the contents of the CD-ROM into a new folder on your PC.
3.
From your PC, double-click the MCW_LINK_DOS.exe file.
4.
Press 1 or 2 on your keyboard to establish which COM port is being
used; a window displays a list of all the registered detectors within
the system and their IDs, as shown in Figure 2.
5.
To view a specific detector ID you should initiate an event, for
example, alarm or tamper (a tamper event is initiated by opening
and closing the cover).
6.
Write down the ID (6 characters, for example, F384B3).
7.
Click X on the top right corner of the window to close the window.
8.
A new window will open; click End Now.
Notes:
a) When receiving and viewing messages on your screen the
software creates a new file in the directory you already opened
containing the MCW_LINK_DOS.exe file and ID_TABLE.txt file.
This new file will contain a name that includes the date of the
received messages, for example, THUSEP23.txt
(day/month/date.txt). This enables the computer to
automatically create a log file of all received messages. Every
day the computer automatically opens a new file with the date
included in the file name.
b) You can convert the .txt data file into an Excel data sheet (.xls)
by clicking File
→
Open then launching the daily file from the
directory to which it was saved. Follow the remainder of the
instructions of the Text Import Wizard.
Figure 2. All Detector ID window
5.2 PowerCode - Viewing Specific
Detector IDs
To view specific detector IDs, you need to enroll the required
detectors by filling a simple .txt file to provide details of the detector
ID.
1.
From your PC, double-click the ID_TABLE.txt file.
Note: If the file opens as Read-only, from Windows Explorer right-
click the file, select Properties, then click the General tab.
Deselect the Read-Only checkbox, then click OK.
2.
Enter the ID of the detector; enter each ID on a separate row.
3.
Save the ID_TABLE.txt file using the same file name (from the
File menu, click Save).
4.
Click X on the top right corner of the window to close the
ID_TABLE.txt window.
5.
Double-click the MCW_LINK_DOS.exe file.
6.
Press 1 or 2 on your keyboard to establish which COM port is
being used; a window displays a list of all the enrolled detectors
and their IDs, as shown in Figure 3.
DE3140U
3
