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Table Of Contents

Contents
- Figures
- Tables
- Revision History
Preface
- P.1 About the EP93xx User’s Guide
- P.2 Related Documents from Cirrus Logic
- P.3 Reference Documents
- P.4 Notational Conventions
- P.5 Register Example
Introduction
- 1.1 Introduction
- 1.2 EP93xx Features
- 1.3 EP93xx Processor Applications
- 1.4 EP93xx Processor Highlights
ARM920T Core and Advanced High-Speed Bus (AHB)
- 2.1 Introduction
- 2.2 Overview: ARM920T Core
- 2.3 AHB Decoder
MaverickCrunch Co-Processor
- 3.1 Introduction
- 3.2 Programming Examples
  - 3.2.1 Example 1
  - 3.2.2 Example 2
    - 3.2.2.1 C Code
    - 3.2.2.2 MaverickCrunch Assembly Language Instructions
- 3.3 DSPSC Register
- 3.4 ARM Co-Processor Instruction Format
- 3.5 Instruction Set for the MaverickCrunch Co-Processor
Boot ROM
- 4.1 Introduction
  - 4.1.1 Boot ROM Hardware Operational Overview
    - 4.1.1.1 Memory Map
  - 4.1.2 Boot ROM Software Operational Overview
- 4.2 Boot Options
System Controller
- 5.1 Introduction
- 5.2 Registers
Vectored Interrupt Controller
- 6.1 Introduction
- 6.2 Registers
Raster Engine With Analog/LCD Integrated Timing and Interface
- 7.1 Introduction
- 7.2 Features
- 7.3 Raster Engine Features Overview
- 7.4 Functional Details
- 7.5 Registers
Graphics Accelerator
- 8.1 Overview
- 8.2 Block Processing Modes
- 8.3 Line Draws
  - 8.3.1 Breshenham Line Draws
  - 8.3.2 Pixel Step Line Draws
- 8.4 Memory Organization for Graphics Accelerator
- 8.5 Register Programming
  - 8.5.1 Word Count
    - 8.5.1.1 Example: 8 BPP mode
    - 8.5.1.2 Example: 24 BPP (packed) mode
  - 8.5.2 Pixel End and Start
- 8.6 Register Usage
- 8.7 Registers
1/10/100 Mbps Ethernet LAN Controller
- 9.1 Introduction
- 9.2 Descriptor Processor
- 9.3 Registers
DMA Controller
- 10.1 Introduction
- 10.2 Registers
  - 10.2.1 DMA Controller Memory Map
  - 10.2.2 Internal M2P/P2M Channel Register Map
Universal Serial Bus Host Controller
- 11.1 Introduction
  - 11.1.1 Features
- 11.2 Overview
- 11.3 Registers
Static Memory Controller
- 12.1 Introduction
- 12.2 Static Memory Controller Operation
- 12.3 PCMCIA Interface (EP9315 Processor Only)
- 12.4 PC Card Memory-Mode Enable Signals
- 12.5 PC Card Memory Mapping
- 12.6 Registers
  - 12.6.1 Bank Configuration Registers
  - 12.6.2 PCMCIA Configuration Registers (EP9315 Processor Only)
SDRAM, SyncROM, and SyncFLASH Controller
- 13.1 Introduction
- 13.2 Booting from SyncROM or SyncFLASH
- 13.3 Address Pin Usage
- 13.4 SDRAM Initialization
- 13.5 Programming Mode Register: SDRAM Or SyncROM Device
- 13.6 SDRAM Self Refresh
  - 13.6.1 Entering Self Refresh Mode
  - 13.6.2 Exiting Self Refresh Mode
- 13.7 Programming Registers: SyncFLASH Device
- 13.8 External Synchronous Memory System
  - 13.8.1 Chip Select SDCSN[3:0] Decoding
  - 13.8.2 Address/Data/Control Required by Memory System
- 13.9 Registers
UART1 With HDLC and Modem Control Signals
- 14.1 Introduction
- 14.2 UART Overview
- 14.3 Modem
- 14.4 HDLC
- 14.5 UART1 Package Dependency
  - 14.5.1 Clocking Requirements
  - 14.5.2 Bus Bandwidth Requirements
- 14.1 Registers
UART2
- 15.1 Introduction
- 15.2 IrDA SIR Block
- 15.3 UART2 Package Dependency
  - 15.3.1 Clocking Requirements
  - 15.3.2 Bus Bandwidth Requirements
- 15.4 Registers
UART3 With HDLC Encoder
- 16.1 Introduction
- 16.2 Implementation Details
- 16.3 Registers
IrDA
- 17.1 Introduction
- 17.2 IrDA Interfaces
- 17.3 Shared IrDA Interface Feature
- 17.4 Medium IrDA Specific Features
  - 17.4.1 Introduction
    - 17.4.1.1 Bit Encoding
    - 17.4.1.2 Frame Format
  - 17.4.2 Functional Description
- 17.5 Fast IrDA Specific Features
- 17.6 Registers
Timers
- 18.1 Introduction
- 18.2 Registers
Watchdog Timer
- 19.1 Introduction
- 19.1 Registers
Real Time Clock With Software Trim
- 20.1 Introduction
  - 20.1.1 Software Trim
  - 20.1.2 Reset Control
- 20.1 Registers
I2S Controller
- 21.1 Introduction
- 21.2 I2S Transmitter Channel Overview
- 21.3 I2S Receiver Channel Overview
  - 21.3.1 Receiver FIFO’s
- 21.4 I2S Master Clock Generation
- 21.5 I2S Bit Clock Rate Generation
  - 21.5.1 Example of the Bit Clock Generation.
  - 21.5.2 Example of Right Justified LRCK format
- 21.6 Interrupts
- 21.7 Registers
AC’97 Controller
- 22.1 Introduction
- 22.2 Interrupts
  - 22.2.1 Channel Interrupts
  - 22.2.2 Global Interrupts
- 22.3 System Loopback Testing
- 22.4 Registers
Synchronous Serial Port
- 23.1 Introduction
- 23.2 Features
- 23.3 SSP Functionality
- 23.4 SSP Pin Multiplex
- 23.5 Configuring the SSP
- 23.6 Registers
Pulse Width Modulator
- 24.1 Introduction
- 24.2 Theory of Operation
  - 24.2.1 PWM Programming Examples
  - 24.2.2 Programming Rules
- 24.3 Registers
Analog Touch Screen Interface
- 25.1 Introduction
- 25.2 Touch Screen Controller Operation
- 25.3 Registers
Keypad Interface
- 26.1 Introduction
- 26.2 Theory of Operation
- 26.3 Registers
IDE Interface
- 27.1 Introduction
- 27.2 Theory of Operation
- 27.3 Registers
GPIO Interface
- 28.1 Introduction
- 28.2 Registers
Security
- 29.1 Introduction
- 29.2 Features
- 29.3 Contact Information
- 29.4 Registers
Glossary
EP93XX Register List

DS785UM1 20-1

Chapter 20

20Real Time Clock With Software Trim

20.1 Introduction

The Real Time Clock (RTC) is a circuit that keeps track of the system date and time. The

RTC operates from the normal device power supply and the 32 kHz input clock. The RTC

circuit operates whenever power is applied to the device and the 32 kHz input clock is

running.

The Real Time Clock section is composed of two blocks - Real Time Clock and the RTC

TRIM.

The RTC module provides second level precision for internal time keeping. In addition, the

block provides an interrupt based on a comparison register. The Real Time Clock block

operates whenever power is applied and the 32 kHz input clock is running. However, the RTC

cannot be used to wake the system via its interrupt when the system is in a STANDBY or

HALT state, where PCLK is inactive.

The RTC TRIM block takes the 32,768 Hz clock from the RTC oscillator and creates a

digitally compensated 1 Hz reference clock for use by the time keeping functions.

Note: The 32,768 Hz clock is referred to as the 32 kHz clock throughout the text.

20.1.1 Software Trim

The Real Time Clock oscillator software compensation circuitry allows software controlled

digital compensation of a 32.768 kHz crystal oscillator. Typically, crystal oscillators must be

externally compensated using discrete components. They are mechanically calibrated during

manufacture. Software controlled digital compensation allows the oscillator to be

electronically calibrated by automatic test equipment during manufacture. The circuit also

enables readjustment in the field under software control.

The RTCSWComp register value is determined by manufacturing during board initialization

to adjust the frequency of the 1 Hz clock. Refer to Section 20.1.1.1 for details on how to

calculate the value in this register. This value is then stored in FLASH memory for retrieval

when the product is first enabled in the field. The compensation values need to be restored

once the RTC is permanently enabled for field use.

The compensation value consists of two parts: a counter preload value to act as an integer

divider, (RTCSWComp.INT[15:0]), and the number of 32.768 kHz clocks to delete on a

periodic interval (RTCSWComp.DEL[4:0]).