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ATMEGA64 Datasheet(PDF) 5 Page - ATMEL Corporation |
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ATMEGA64 Datasheet(HTML) 5 Page - ATMEL Corporation |
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5 / 20 page  5 ATmega64(L) 2490F–AVR–12/03 ATmega103 Compatibility Mode By programming the M103C Fuse, the ATmega64 will be compatible with the ATmega103 regards to RAM, I/O pins and Interrupt Vectors as described above. How- ever, some new features in ATmega64 are not available in this compatibility mode, these features are listed below: • One USART instead of two, asynchronous mode only. Only the eight least significant bits of the Baud Rate Register is available. • One 16 bits Timer/Counter with two compare registers instead of two 16 bits Timer/Counters with three compare registers. • Two-wire serial interface is not supported. • Port G serves alternate functions only (not a general I/O port). • Port F serves as digital input only in addition to analog input to the ADC. • Boot Loader capabilities is not supported. • It is not possible to adjust the frequency of the internal calibrated RC Oscillator. • The External Memory Interface can not release any Address pins for general I/O, neither configure different wait states to different External Memory Address sections. • Only EXTRF and PORF exist in the MCUCSR Register. • No timed sequence is required for Watchdog Timeout change. • Only low-level external interrupts can be used on four of the eight External Interrupt sources. • Port C is output only. • USART has no FIFO buffer, so Data OverRun comes earlier. • The user must have set unused I/O bits to 0 in ATmega103 programs. Pin Descriptions VCC Digital supply voltage. GND Ground. Port A (PA7..PA0) Port A is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port A output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port A pins that are externally pulled low will source current if the pull-up resistors are activated. The Port A pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port A also serves the functions of various special features of the ATmega64 as listed on page 71. Port B (PB7..PB0) Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port B output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port B also serves the functions of various special features of the ATmega64 as listed on page 72. |
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