====== Backup Battery ======

===== CB290 / CB405 =====

When a supercapacitor is connected to VBB, the memory can be maintained
anywhere from a couple days to a couple weeks once powered off.   The
CB290/CB405 consumes about 15-20mA of current when idling.   For a
longer backup period, a battery pack can be used.  A protection diode, as
shown below, is necessary when using a battery, as the device normally
attempts to charge a capacitor through VBB.   Due to the relatively high
standby current for battery backup, it is recommended to keep the device
powered if possible and only maintain battery backup for short periods in
the case of an emergency.

{{ :cubloc:connecting_a_backup_battery_to_cb290_cb405:backupbattery.png? }}

==== Power Features ====
  * Operating Voltage : 4.5V  to  5.5V
  * Operating Clock : 18.432MHz
  * I/O Port Source Current : 20mA
  * I/O Port Sink Current : 25mA
  * Operating Temperature : -40 to 125 Degrees(Celcius)
  * Maintenance Temperature: -60 to 140 Degrees(Celcius)
  * Operating Humidity : 5 to 95% RH (Keep the board's surface dry when in use)

==== Additional Information ====
If a CUBLOC module is supplied with power above the recommended voltage,
the device can be destroyed. Also please be careful to avoid electrostatic
discharge, as it too can destroy the device. Please be aware that P1 is an
input-only pin.  To reduce accidental power drain, please set unused pins to
input.  All I/O ports are set to input as default at power on. When not using
SIN, SOUT, and ATN, please do not connect them to anything.

===== CT1721C =====

The CT1721C will maintain data in its volatile memory when powered off by using a backup battery. If backup is not needed, the program should clear the memory at the beginning of the program.

<code xbasic>
Const Device = CT1720
Dim TX1 As Integer, TY1 As Integer
TY1 = 0       ' Clear only TY1
</code>

Use [[cubloc:ramclear:index|RamClear]] to clear all data memory at the start of your program.

<code xbasic>
Const Device = CT1720
Dim TX1 As Integer, TY1 As Integer
RamClear      ' Clear all RAM, both TX1 and TY2
</code>

To add a backup battery to the CT1721C, connect a 3V battery to the "Batt. Backup" terminal on the back, bottom right side of the CT1721C and leave the "JUMPER_SUPERCAP" open.  To use a super capacitor instead of battery, connect the super capacitor to "Batt. Backup" and short the "JUMPER_SUPERCAP" terminal to enable charging while the power is on.

{{ :cubloc:connecting_a_backup_battery_to_cb290_cb405:cutouch_battery.png }}

In Ladder Logic, all registers S, M, C, T, and D are retained by the backup battery. Register P is cleared by default when the device is powered on. If you only want to clear parts of a register, rather than all registers, use the following method:

<code xbasic>
Const Device = CT1720
Dim i As Integer
For i=0 to 32   ' Clear only M0 to M32
 _M(i) = 0
Next
Set Ladder On
</code>

[[cubloc:index|CUBLOC - Embedded Controller]]