MAX32600 User’s Guide
System Clock, Timers/Counters, Watchdog Timers and Real Time Clock
10.3 Real Time Clock (RTC)
The PRESCALE==0h setting represents the minimum prescale reload value, which means that the RTC timer will be incremented each 4kHz clock period. This is
also reflected in the value in the ’4kHz ticks in LSB’ column above. Setting PRESCALE==1h will then give the RTC timer a resolution of (2/4kHz) and a tick frequency
of 2048Hz, etc.
Setting PRESCALE=0h gives the RTC timer its fastest possible frequency (4096Hz), causing it to reach its maximum value of FFFFFFFFh and roll over in 1048576
seconds (2
32
/ 4096), or approximately 12 days. Setting the maximum prescale value of PRESCALE=Ch results in the slowest possible RTC timer frequency of 1Hz,
causing it to reach its maximum value of FFFFFFFFh and roll over in 2
32
seconds, or about 139.6 years.
The prescaler range is intentionally wide to allow for a variety of potential applications. If the intent of the RTC for a particular application is to measure time across
a long device lifetime, then a long period makes the most sense. If the RTC will instead be used to measure events and time intervals of shorter duration, then a
shorter period (and a smaller prescaler value) will reduce the maximum time value the RTC can contain but will increase the effective resolution of the RTC timer to
allow shorter intervals of time to be measured (or to allow RTC timer-based wakeup operations to occur more precisely).
Starting the RTC Timer
Once the RTC timer has been properly configured, it can be started by setting the
bit to 1. This will cause the RTC timer to begin counting
based on the selected prescaler rate.
10.3.5
Registers (RTCTMR)
10.3.5.1
Module RTCTMR Registers
Address
Register
32b
Word Len
Description
0x40090A00
1
RTC Timer Control
0x40090A04
1
RTC Timer Count Value
0x40090A08
1
RTC Time of Day Alarm 0 Compare Register
0x40090A0C
1
RTC Time of Day Alarm 1 Compare Register
0x40090A10
1
CPU Interrupt and RTC Domain Flags
0x40090A18
1
Interrupt Enable Controls
0x40090A1C
1
RTC Timer Prescale Setting
0x40090A24
1
RTC Timer Prescale Compare Mask
0x40090A28
1
RTC Timer Trim Controls
Rev.1.3 April 2015
Maxim Integrated
Page 568
