- •Features
- •Pin Configurations
- •Disclaimer
- •Overview
- •Block Diagram
- •AT90S8535 Compatibility
- •Pin Descriptions
- •Port A (PA7..PA0)
- •Port B (PB7..PB0)
- •Port C (PC7..PC0)
- •Port D (PD7..PD0)
- •RESET
- •XTAL1
- •XTAL2
- •AVCC
- •AREF
- •AVR CPU Core
- •Introduction
- •Architectural Overview
- •Status Register
- •Stack Pointer
- •Interrupt Response Time
- •SRAM Data Memory
- •Data Memory Access Times
- •EEPROM Data Memory
- •EEPROM Read/Write Access
- •I/O Memory
- •Clock Systems and their Distribution
- •CPU Clock – clkCPU
- •I/O Clock – clkI/O
- •Flash Clock – clkFLASH
- •ADC Clock – clkADC
- •Clock Sources
- •Default Clock Source
- •Crystal Oscillator
- •External RC Oscillator
- •External Clock
- •Timer/Counter Oscillator
- •Idle Mode
- •Power-down Mode
- •Power-save Mode
- •Standby Mode
- •Extended Standby Mode
- •Analog-to-Digital Converter
- •Analog Comparator
- •Brown-out Detector
- •Internal Voltage Reference
- •Watchdog Timer
- •Port Pins
- •Resetting the AVR
- •Reset Sources
- •Power-on Reset
- •External Reset
- •Brown-out Detection
- •Watchdog Reset
- •Watchdog Timer
- •Timed Sequences for Changing the Configuration of the Watchdog Timer
- •Safety Level 0
- •Safety Level 1
- •Safety Level 2
- •Interrupts
- •I/O-Ports
- •Introduction
- •Configuring the Pin
- •Reading the Pin Value
- •Unconnected pins
- •Alternate Port Functions
- •Alternate Functions of Port A
- •Alternate Functions Of Port B
- •Alternate Functions of Port C
- •Alternate Functions of Port D
- •Port A Data Register – PORTA
- •Port B Data Register – PORTB
- •Port C Data Register – PORTC
- •Port D Data Register – PORTD
- •External Interrupts
- •8-bit Timer/Counter0 with PWM
- •Overview
- •Registers
- •Definitions
- •Counter Unit
- •Output Compare Unit
- •Force Output Compare
- •Modes of Operation
- •Normal Mode
- •Fast PWM Mode
- •Phase Correct PWM Mode
- •Internal Clock Source
- •Prescaler Reset
- •External Clock Source
- •16-bit Timer/Counter1
- •Overview
- •Registers
- •Definitions
- •Compatibility
- •Counter Unit
- •Input Capture Unit
- •Input Capture Trigger Source
- •Noise Canceler
- •Using the Input Capture Unit
- •Output Compare Units
- •Force Output Compare
- •Modes of Operation
- •Normal Mode
- •Fast PWM Mode
- •Phase Correct PWM Mode
- •8-bit Timer/Counter2 with PWM and Asynchronous Operation
- •Overview
- •Registers
- •Definitions
- •Counter Unit
- •Output Compare Unit
- •Force Output Compare
- •Modes of Operation
- •Normal Mode
- •Fast PWM Mode
- •Phase Correct PWM Mode
- •Timer/Counter Prescaler
- •Slave Mode
- •Master Mode
- •SPI Control Register – SPCR
- •SPI Status Register – SPSR
- •SPI Data Register – SPDR
- •Data Modes
- •USART
- •Overview
- •AVR USART vs. AVR UART – Compatibility
- •Clock Generation
- •External Clock
- •Synchronous Clock Operation
- •Frame Formats
- •Parity Bit Calculation
- •USART Initialization
- •Sending Frames with 5 to 8 Data Bits
- •Sending Frames with 9 Data Bits
- •Parity Generator
- •Disabling the Transmitter
- •Receiver Error Flags
- •Parity Checker
- •Disabling the Receiver
- •Flushing the Receive Buffer
- •Asynchronous Data Recovery
- •Using MPCM
- •Write Access
- •Read Access
- •Two-wire Serial Interface
- •Features
- •TWI Terminology
- •Electrical Interconnection
- •Transferring Bits
- •START and STOP Conditions
- •Address Packet Format
- •Data Packet Format
- •Overview of the TWI Module
- •SCL and SDA Pins
- •Bit Rate Generator Unit
- •Bus Interface Unit
- •Address Match Unit
- •Control Unit
- •TWI Register Description
- •TWI Bit Rate Register – TWBR
- •TWI Control Register – TWCR
- •TWI Status Register – TWSR
- •TWI Data Register – TWDR
- •Using the TWI
- •Transmission Modes
- •Master Transmitter Mode
- •Master Receiver Mode
- •Slave Receiver Mode
- •Slave Transmitter Mode
- •Miscellaneous States
- •Analog Comparator
- •Analog Comparator Multiplexed Input
- •Features
- •Operation
- •Starting a Conversion
- •Differential Gain Channels
- •Changing Channel or Reference Selection
- •ADC Input Channels
- •ADC Voltage Reference
- •ADC Noise Canceler
- •Analog Input Circuitry
- •ADC Accuracy Definitions
- •ADC Conversion Result
- •ADLAR = 0
- •ADLAR = 1
- •Boot Loader Features
- •Application Section
- •BLS – Boot Loader Section
- •Boot Loader Lock Bits
- •Performing a Page Write
- •Using the SPM Interrupt
- •Setting the Boot Loader Lock Bits by SPM
- •Reading the Fuse and Lock Bits from Software
- •Preventing Flash Corruption
- •Simple Assembly Code Example for a Boot Loader
- •Fuse Bits
- •Latching of Fuses
- •Signature Bytes
- •Calibration Byte
- •Signal Names
- •Parallel Programming
- •Enter Programming Mode
- •Chip Erase
- •Programming the Flash
- •Programming the EEPROM
- •Reading the Flash
- •Reading the EEPROM
- •Programming the Lock Bits
- •Reading the Signature Bytes
- •Reading the Calibration Byte
- •Serial Downloading
- •Data Polling Flash
- •Data Polling EEPROM
- •Electrical Characteristics
- •External Clock Drive Waveforms
- •External Clock Drive
- •Two-wire Serial Interface Characteristics
- •ADC Characteristics – Preliminary Data
- •Instruction Set Summary
- •Ordering Information(1)
- •Packaging Information
- •Data Sheet Change Log for ATmega8535
- •Changes from Rev. 2502A-06/02 to Rev. 2502B-09/02
- •Table of Contents
ATmega8535(L)
Pin Descriptions
VCC |
Digital supply voltage. |
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GND |
Ground. |
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Port A (PA7..PA0) |
Port A serves as the analog inputs to the A/D Converter. |
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Port A also serves as an 8-bit bi-directional I/O port, if the A/D Converter is not used. |
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Port pins can provide internal pull-up resistors (selected for each bit). The Port A output |
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buffers have symmetrical drive characteristics with both high sink and source capability. |
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When pins PA0 to PA7 are used as inputs and are externally pulled low, they will source |
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current if the internal pull-up resistors are activated. The Port A pins are tri-stated when |
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a reset condition becomes active, even if the clock is not running. |
Port B (PB7..PB0) |
Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each |
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bit). The Port B output buffers have symmetrical drive characteristics with both high sink |
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and source capability. As inputs, Port B pins that are externally pulled low will source |
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current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset |
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condition becomes active, even if the clock is not running. |
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Port B also serves the functions of various special features of the ATmega8535 as listed |
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on page 57. |
Port C (PC7..PC0) |
Port C is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each |
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bit). The Port C output buffers have symmetrical drive characteristics with both high sink |
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and source capability. As inputs, Port C pins that are externally pulled low will source |
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current if the pull-up resistors are activated. The Port C pins are tri-stated when a reset |
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condition becomes active, even if the clock is not running. |
Port D (PD7..PD0) |
Port D is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each |
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bit). The Port D output buffers have symmetrical drive characteristics with both high sink |
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and source capability. As inputs, Port D pins that are externally pulled low will source |
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current if the pull-up resistors are activated. The Port D pins are tri-stated when a reset |
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condition becomes active, even if the clock is not running. |
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Port D also serves the functions of various special features of the ATmega8535 as listed |
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on page 61. |
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Reset input. A low level on this pin for longer than the minimum pulse length will gener- |
RESET |
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ate a reset, even if the clock is not running. The minimum pulse length is given in Table |
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15 on page 35. Shorter pulses are not guaranteed to generate a reset. |
XTAL1 |
Input to the inverting Oscillator amplifier and input to the internal clock operating circuit. |
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XTAL2 |
Output from the inverting Oscillator amplifier. |
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AVCC |
AVCC is the supply voltage pin for Port A and the A/D Converter. It should be externally |
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connected to VCC, even if the ADC is not used. If the ADC is used, it should be con- |
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nected to VCC through a low-pass filter. |
AREF |
AREF is the analog reference pin for the A/D Converter. |
5
2502B–AVR–09/02