Datasheet AT90S4433, AT90LS4433 (Atmel) - 30

External Interrupts
The External Interrupts are triggered by the INT1 and INT0 pins. Observe that, if enabled, the interrupts will trigger even if the INT0/INT1 pins are configured as outputs. This feature provides a way of generating a software interrupt. The External Interrupts can be triggered by a falling or rising edge or a low level. This is set up as indicated in the specification for the MCU Control Register (MCUCR). When the External Interrupt is enabled and is configured as level triggered, the interrupt will trigger as long as the pin is held low. The External Interrupts are set up as described in the specification for the MCU Control Register (MCUCR).
Interrupt Response Time
The interrupt execution response for all the enabled AVR interrupts is four clock cycles minimum. Four clock cycles after the Interrupt Flag has been set, the Program Vector address for the actual interrupt handling routine is executed. During this four clock cycle period, the Program Counter (two bytes) is pushed onto the Stack, and the Stack Pointer is decremented by two. The vector is normally a relative jump to the interrupt routine, and this jump takes two clock cycles. If an interrupt occurs during execution of a multi-cycle instruction, this instruction is completed before the interrupt is served. A return from an interrupt handling routine (same as for a subroutine call routine) takes four clock cycles. During these four clock cycles, the Program Counter (two bytes) is popped back from the Stack, the Stack Pointer is incremented by two and the I-flag in SREG is set. When the AVR exits from an interrupt, it will always return to the main pro- gram and execute one more instruction before any pending interrupt is served.
MCU Control Register –
The MCU Control Register contains control bits for general MCU functions.
MCUCR
Bit 7 6 5 4 3 2 1 0 $35 ($55)
– – SE SM ISC11 ISC10 ISC01 ISC00 MCUCR
Read/Write R R R/W R/W R/W R/W R/W R/W Initial Value 0 0 0 0 0 0 0 0
• Bits 7, 6 – Res: Reserved Bits
These bits are reserved bits in the AT90S4433 and always read as zero.
• Bit 5 – SE: Sleep Enable
The SE bit must be set (one) to make the MCU enter the sleep mode when the SLEEP instruction is executed. To avoid having the MCU entering the sleep mode unless it is the programmer’s purpose, it is recommended that the Sleep Enable SE bit be set just before the execution of the SLEEP instruction.
• Bit 4 – SM: Sleep Mode
This bit selects between the two available sleep modes. When SM is cleared (zero), Idle mode is selected as sleep mode. When SM is set (one), Power-down mode is selected as sleep mode. For details, refer to the paragraph “Sleep Modes” below.
30 AT90S/LS4433
1042H–AVR–04/03 Document Outline Features Pin Configurations Description Block Diagram Pin Descriptions VCC GND Port B (PB5..PB0) Port C (PC5..PC0) Port D (PD7..PD0) RESET XTAL1 XTAL2 AVCC AREF AGND Clock Options Crystal Oscillator External Clock Architectural Overview General Purpose Register File X-register, Y-register and Z- register ALU – Arithmetic Logic Unit In-System Programmable Flash Program Memory SRAM Data Memory Program and Data Addressing Modes Register Direct, Single Register Rd Register Direct, Two Registers Rd and Rr I/O Direct Data Direct Data Indirect with Displacement Data Indirect Data Indirect with Pre- decrement Data Indirect with Post- increment Constant Addressing Using the LPM Instruction Indirect Program Addressing, IJMP and ICALL Relative Program Addressing, RJMP and RCALL EEPROM Data Memory Memory Access Times and Instruction Execution Timing I/O Memory Status Register – SREG Stack Pointer – SP Reset and Interrupt Handling Reset Sources Power-on Reset External Reset Brown-out Detection Watchdog Reset MCU Status Register – MCUSR Interrupt Handling General Interrupt Mask Register – GIMSK General Interrupt Flag Register – GIFR Timer/Counter Interrupt Mask Register – TIMSK Timer/Counter Interrupt Flag Register – TIFR External Interrupts Interrupt Response Time MCU Control Register – MCUCR Sleep Modes Idle Mode Power-down Mode Timer/Counters Timer/Counter Prescaler 8-bit Timer/Counter0 Timer/Counter0 Control Register – TCCR0 Timer Counter0 – TCNT0 16-bit Timer/Counter1 Timer/Counter1 Control Register A – TCCR1A Timer/Counter1 Control Register B – TCCR1B Timer/Counter1 – TCNT1H and TCNT1L Timer/Counter1 Output Compare Register – OCR1H and OCR1L Timer/Counter1 Input Capture Register – ICR1H and ICR1L Timer/Counter1 in PWM Mode Watchdog Timer Watchdog Timer Control Register – WDTCR EEPROM Read/Write Access EEPROM Address Register – EEAR EEPROM Data Register – EEDR EEPROM Control Register – EECR Prevent EEPROM Corruption Serial Peripheral Interface – SPI SS Pin Functionality Data Modes SPI Control Register – SPCR SPI Status Register – SPSR SPI Data Register – SPDR UART Data Transmission Data Reception Multi-processor Communication Mode UART Control UART I/O Data Register – UDR UART Control and Status Register A – UCSRA UART Control and Status Register B – UCSRB Baud Rate Generator UART Baud Rate Register – UBRR Analog Comparator Analog Comparator Control and Status Register – ACSR Analog-to-Digital Converter Features Operation Prescaling ADC Noise Canceler Function ADC Multiplexer Select Register – ADMUX ADC Control and Status Register – ADCSR ADC Data Register – ADCL AND ADCH Scanning Multiple Channels ADC Noise Canceling Techniques ADC Characteristics TA = -40°C to 85°C I/O Ports Port B Port B Data Register – PORTB Port B Data Direction Register – DDRB Port B Input Pins Address – PINB Port B as General Digital I/O Alternate Functions of Port B Port C Port C Data Register – PORTC Port C Data Direction Register – DDRC Port C Input Pins Address – PINC Port C as General Digital I/O Port C Schematics Port D Port D Data Register – PORTD Port D Data Direction Register – DDRD Port D Input Pins Address – PIND Port D as General Digital I/O Alternate Functions of Port D Port D Schematics Memory Programming Program and Data Memory Lock Bits Fuse Bits Signature Bytes Programming the Flash and EEPROM Parallel Programming Signal Names Enter Programming Mode Chip Erase Programming the Flash Reading the Flash Programming the EEPROM Reading the EEPROM Programming the Fuse Bits Programming the Lock Bits Reading the Fuse and Lock Bits Reading the Signature Bytes Parallel Programming Characteristics Serial Downloading Serial Programming Algorithm Data Polling EEPROM Data Polling Flash Serial Programming Characteristics Electrical Characteristics Absolute Maximum Ratings* DC Characteristics External Clock Drive Waveforms Typical Characteristics Register Summary Instruction Set Summary Ordering Information Packaging Information 32A 28P3 Errata for AT90S/LS4433 Rev. Rev. C/D/E/F Data Sheet ChangeLog for AT90S/LS4433 Changes from Rev. 1042E-09/01 to Ref. 1042F-03/02 Changes from Rev. 1042F-03/02 to Ref. 1042G-09/02 Changes from Rev. 1042G-09/02 to Ref. 1042H-04/03 Table of Contents