Port C Port C is an 8-bit bi-directional I/O port. Three I/O memory address locations are allocated for the Port C, one each for the Data Register - PORTC, $15($35), Data Direction Register - DDRC, $14($34) and the Port C Input Pins - PINC, $13($33). The Port C Input Pins address is read only, while the Data Register and the Data Direction Register are read/write. All port pins have individually selectable pull-up resistors. The Port C output buffers can sink 20mA and thus drive LED dis- plays directly. When pins PC0 to PC7 are used as inputs and are externally pulled low, they will source current if the internal pull-up resistors are activated. Port C Data Register - PORTC Bit 7 6 5 4 3 2 1 0 $15 ($35) PORTC7PORTC6PORTC5PORTC4PORTC3PORTC2PORTC1PORTC0PORTC Read/Write R/W R/W R/W R/W R/W R/W R/W R/W Initial value 0 0 0 0 0 0 0 0 Port C Data Direction Register - DDRC Bit 7 6 5 4 3 2 1 0 $14 ($34) DDC7DDC6DDC5DDC4DDC3DDC2DDC1DDC0DDRC Read/Write R/W R/W R/W R/W R/W R/W R/W R/W Initial value 0 0 0 0 0 0 0 0 Port C Input Pins Address - PINC Bit 7 6 5 4 3 2 1 0 $13 ($33) PINC7PINC6PINC5PINC4PINC3PINC2PINC1PINC0PINC Read/Write R R R R R R R R Initial value Hi-Z Hi-Z Hi-Z Hi-Z Hi-Z Hi-Z Hi-Z Hi-Z The Port C Input Pins address - PINC - is not a register, and this address enables access to the physical value on each Port C pin. When reading PORTC, the Port C Data Latch is read, and when reading PINC, the logical values present on the pins are read. Port C As General Digital I/O All 8 pins in Port C have equal functionality when used as digital I/O pins. PCn, General I/O pin: The DDCn bit in the DDRC register selects the direction of this pin, if DDCn is set (one), PCn is con- figured as an output pin. If DDCn is cleared (zero), PCn is configured as an input pin. If PORTCn is set (one) when the pin configured as an input pin, the MOS pull up resistor is activated. To switch the pull up resistor off, PORTCn has to be cleared (zero) or the pin has to be configured as an output pin.The port pins are tristated when a reset condition becomes active, even if the clock is not running. Table 32. DDCn Effects on PORT C Pins DDCnPORTCnI/OPull UpComment 0 0 Input No Tri-state (Hi-Z) 0 1 Input Yes PCn will source current if ext. pulled low. 1 0 Output No Push-Pull Zero Output 1 1 Output No Push-Pull One Output n: 7…0, pin number 74AT90S/LS4434 and AT90S/LS8535 Document Outline Features Description Block Diagram Comparison between AT90S4434 and AT90S8535 Pin Descriptions VCC GND Port A (PA7..PA0) Port B (PB7..PB0) Port C (PC7..PC0) Port D (PD7..PD0) RESET XTAL1 XTAL2 AVCC AREF AGND Clock Options Crystal Oscillator External Clock Timer Oscillator 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 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 Power Save Mode Timer / Counters Timer/Counter Prescalers 8-bit Timer/Counter0 Timer/Counter0 Control Register - TCCR0 Timer Counter 0 - 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 - OCR1AH AND OCR1AL Timer/Counter1 Output Compare Register - OCR1BH AND OCR1BL Timer/Counter1 Input Capture Register - ICR1H AND ICR1L Timer/Counter1 In PWM Mode 8-bit Timer/Counter 2 Timer/Counter2 Control Register - TCCR2 Timer/Counter2 - TCNT2 Timer/Counter2 Output Compare Register - OCR2 Timer/Counter 2 in PWM mode Asynchronous Status Register - ASSR Asynchronous Operation of Timer/Counter2 Watchdog Timer Watchdog Timer Control Register - WDTCR EEPROM Read/Write Access EEPROM Address Register - EEARH and EEARL 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 UART Control UART I/O Data Register - UDR UART Status Register - USR UART Control Register - UCR Baud Rate Generator UART Baud Rate Register - UBRR Analog Comparator Analog Comparator Control And Status Register - ACSR Analog to Digital Converter 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 I/O-Ports Port A Port A Data Register - PORTA Port A Data Direction Register - DDRA Port A Input Pins Address - PINA Port A as General Digital I/O Port A Schematics 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 B Schematics 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 Alternate Functions of Port C 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 (Continued) Instruction Set Summary (Continued) Ordering Information Pin Configurations
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