Model CXT-IR
CXT-IR Instruction Manual
Rev. 2.1
Page 34 of 48
4.2.2
CXT Transceiver Registers
4.2.2.1
Battery Info – Multiple Registers
If a Detcon smart battery pack is connected to the CXT, there are five registers associated with information about
that battery. The CXT utilizes the I
2
C interface to read battery status and only one Detcon battery pack can be
read per CXT.
The controller can determine if a battery is present by reading the Status Register (register 8204). There are two
bits in this sixteen bit register pertaining to the battery, Battery Detect – bit 4 (lowest bit is 0) and Battery Fault
– bit 5. Both bits default to a value of 0. Battery Detect will be set once the first read of the battery over the I
2
C
interface was successful. Battery Fault will be set if a battery was detected but the last read failed. Battery Fault
is re-evaluated upon every read of the battery which is set to approximately every 5 seconds. Register 8206 (I
2
C
Batt Read Fails) will increment by 4 each time there is a failure since there are 4 attempts before declaring
failure. This register can be cleared by writing a 0 to it at any point.
Once the battery has been detected the controller can read the battery life (registers 8199 and 8200). The battery
adjusts these values based upon the average current usage. If this usage varies widely over time it will take some
time to re-adjust the battery life readings. For instance an Alarm Station with no alarms will consume a very
small amount of battery but when Alarms are active this will jump to a much higher level of usage. So in this
case battery life may go from several weeks down to several hours.
The battery life is presented in two forms, life remaining in percentage (register 8199) and life remaining in
minutes (register 8200). The battery Life remaining is percentage is a value between 0 and 100 and battery life
in minutes is an unsigned value between 0 and 65535. Both readings are generally necessary to provide
appropriate feedback to the user. Life in minutes is the best for determining when to change the battery. For
example if the user wanted to be notified a day before the battery needed to be changed, the user could set a
threshold in the controller to be notified of low battery after 1440 minutes (1 day).
Since 65535 is the maximum value for life remaining in minutes, this represents a maximum of 45.5 days. The
battery life for an application can be much greater than this value and will remain at a reading of 65535 until it
drops below this. Life in percentage was added for this reason. Percentage will track starting at 100 percent
and drop down as battery life decreases. The controller can therefore use both registers, one to represent usage
in percentage to present to the user and then use the life in minutes to set a threshold on when a low battery
condition exists for changing the battery.
4.2.2.2
Wireless Controller Version
This is set to a value based upon the version of firmware programmed into the RXT-320 microcontroller. It is
stored as two byte value representing the major and minor revision numbers. So a 0113h (275 decimal) represents
a major version of 01 and minor version of 13. As software is updated this will be incremented appropriately.
4.2.2.3
Register – Update Rate
The update rate represents the amount of time in seconds the CXT transceiver will be in a low power state. Its
main purpose is to provide a mechanism to place all wireless transceivers in a system into a low power mode to
conserve battery power. If there are no batteries used within the network of wireless transceivers this register
would not be utilized.
Upon power up, this register is set to 0 and the CXT transceiver is not in low power mode. To place a network
to low power mode the controller will generate a broadcast request (Modbus™ address = 0) and do a single write
(function code 06) to register 8202 with the number of seconds the network should go into low power mode.
