
User’s Manual U14272EJ3V0UM
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CHAPTER 11 REALTIME CLOCK UNIT (RTC)
This chapter describes the RTC unit’s operations and register settings.
11.1 General
The RTC unit has a total of three timers, including the following two types.
RTCLong .......... This is a 24-bit programmable counter that counts down by 32.768 kHz clock cycle. Cycle
interrupts can be occurred for up to every 512 seconds. The RTC unit of the V
R
4181 includes
two RTCLong timers.
ElapsedTime..... This is a 48-bit up counter that counts up by 32.768 kHz clock cycle. It counts up to 272 years
before returning to zero. It includes 48-bit comparator (ECMPLREG, ECMPMREG, and
ECMPHREG) and 48-bit alarm time register (ETIMELREG, ETIMEMREG, and ETIMEHREG)
to enable interrupts to occur at specified times.
11.2 Register Set
The RTC registers are listed below.
Table 11-1. RTC Registers
Physical address
R/W
Register symbol
Function
0x0B00 00C0
R/W
ETIMELREG
ElapsedTime L register
0x0B00 00C2
R/W
ETIMEMREG
ElapsedTime M register
0x0B00 00C4
R/W
ETIMEHREG
ElapsedTime H register
0x0B00 00C8
R/W
ECMPLREG
ElapsedTime compare L register
0x0B00 00CA
R/W
ECMPMREG
ElapsedTime compare M register
0x0B00 00CC
R/W
ECMPHREG
ElapsedTime compare H register
0x0B00 00D0
R/W
RTCL1LREG
RTCLong1 L register
0x0B00 00D2
R/W
RTCL1HREG
RTCLong1 H register
0x0B00 00D4
R
RTCL1CNTLREG
RTCLong1 count L register
0x0B00 00D6
R
RTCL1CNTHREG
RTCLong1 count H register
0x0B00 00D8
R/W
RTCL2LREG
RTCLong2 L register
0x0B00 00DA
R/W
RTCL2HREG
RTCLong2 H register
0x0B00 00DC
R
RTCL2CNTLREG
RTCLong2 count L register
0x0B00 00DE
R
RTCL2CNTHREG
RTCLong2 count H register
0x0B00 01DE
R/W
RTCINTREG
RTC interrupt register
Each register is described in detail below.