Revision as of 15:42, 16 June 2015

Objective

In this tutorial we will be discussing about the internal RTC of LPC1768. We will see what are the different registers associated with the RTC but we will mainly focus on basics registers required to use RTC. Later we will see how to use Explore Embedded library for RTC.

RTC Registers

The RTC includes a number of registers. We will concentrate some of the basic required registers.

RTC Register Configuration

Lets see how to configure these registers.

CCR ( Clock Control Register )

The Clock Control Register register controls the operation of the clock divide circuit.

Bit 0 – CLKEN : Clock Enable
This bit is written with one to enable time counters and written with zero to disable time counters.

Bit 1 - CTCRST : CTC Reset
When this bit is set to one, the internal oscillator divider are reset.

Bit 3:2 - Reserved
These bits must be set to zero for normal RTC operation.

Bit 4 - CCALEN : Calibration counter enable
To disable calibration counter and reset it to zero, write one to this bit. When written zero, the counter is enabled and starts counting

Bit 31:5 - Reserved

Time Counter Register

The time value consists of the eight counters and there is separate register associated with each counter. To update the RTC, new values should be written to these registers.

Consolidated Time Registers

The values of the Time Counters can optionally be read in a consolidated format which allows the programmer to read all time counters with only three read operations.

There are 3 Consolidated Time Registers. The minimum and maximum values of the various fields in these registers are same as the respective Time Counter Register.

These registers are read only. New values should be written to Time Counter Registers.

Consolidated Time Register 0 (CTIME0)

Consolidated Time Register 1 (CTIME1) Consolidated Time Register 2 (CTIME2)

Steps for Configuring RTC

Code EXample

Example 1

Using Explore Embedded Liberaries