CONFIDENTIAL
DM816x RTC User Guide v1.1
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Z3 Technology, LLC
♦
100 N. 8th St., Suite 250
♦
Lincoln, NE 68508 USA
♦
+1.402.323.0702
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1
Introduction
The DM8148, DM8168, and DM8169 modules from Z3 Technology contain a real time clock circuit that can be used to
keep the time and date even when power is removed. The RTC uses a CR1220 or CR1225 lithium battery connected to
the module (the CR1225 will provide slightly more power).
In order for this hardware real time clock to function, the proper firmware needs to be loaded into the MSP430. The
modules do NOT have this firmware loaded prior to leaving the factory. In order to enable the RTC function, the RTC
firmware needs to be uploaded to the module. This document describes how to do this.
2
The RTC
3.1 RTC Battery
The RTC firmware controls the power drain on the RTC battery. Without the proper RTC firmware loaded, the RTC
battery will be drained very quickly -- in a matter of minutes.
Do not insert a battery in the battery holder before the RTC firmware is loaded, or the battery will be lost
. Please
wait until after the RTC software is installed before inserting the battery in the battery holder. The battery should last for
3 to 5 years in normal conditions.
3.1 RTC Power
The RTC can receive power from the main module power, the RTC battery, or from the expansion connector J5 pin 83.
Regardless of a battery being present, the RTC circuit will receive power from the main module any time the +12V
power is applied. This is true even if the power switch is OFF on modules that have a power switch. Whenever there is
no +12V power applied to the module, then either the RTC battery or J5 pin 83 will be able to power the RTC.
J5 pin 83 can be used to connect a battery with longer life than the CR1220/1225 or if the battery needs to be assembled
on the application board.
