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Real Time Clock (RTC)
The CPU includes a low drift RTC. The date and time are retained using an on-board
rechargeable lithium battery.
The CPU date and time can be set using the ACE3600 STS. The CPU can also be
synchronized with other RTUs in the system, using the system clock. For more information,
see the Setting/Getting a Site's Date and Time section or the Creating a User Application
section of the ACE3600 STS User Guide.
Backup Battery for SRAM and RTC
The CPU module includes a rechargeable lithium battery that provides backup power and data
retention for the SRAM and RTC.
The lithium battery is located on the CPU board and cannot be replaced.
Typically, the battery in the CPU 3680 will retain the SRAM data and RTC for 40 continuous
days, and the battery in the CPU 3640/3610 will retain the SRAM data and RTC for 60
continuous days, without power and no Lead-Acid backup battery. When the SRAM option is
not used, the Lithium battery will keep the Real Time Clock running for a longer period of
time.
CPU with Security
In an ACE3600 system with security, the CPU 3680 has a dedicated security hardware
repository. Backup power and data retention for this repository is also provided by the
rechargeable lithium battery.
For more information on the security repository, see the ACE3600 Advanced System Security
User Guide.
Redundant CPU
CPU redundancy (ACE3680 only) ensures continuous RTU operation if one CPU fails. For
details on the redundant CPU, see Appendix E: CPU and Power Supply Redundancy below.
CPU Firmware and Operation Modes
The CPU firmware is a real-time multitasking operating system, based on the Wind River
VxWorks OS. The CPU shipped from the factory with the most recent firmware version, and
it can be updated/replaced using a remote or local connection. Downloading firmware updates
is performed using the STS. (See Downloading to a Site in the ACE3600 STS manual.) If the
new firmware download stops or fails, the CPU will restart with the existing firmware.
4-5
CPU Module
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