ATMEGA48 20PU PDF

Posted in: Uncategorized. Leave a comment The following is a small tutorial on how to set low fuse byte to modify the clock speed of a factory fresh Atmegapu microprocessor. First check the initial factory fuse settings with avrdude. This is needed because the Atmega48 initially runs at 1MHz and is therefore to slow for the programmer.

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Posted in: Uncategorized. Leave a comment The following is a small tutorial on how to set low fuse byte to modify the clock speed of a factory fresh Atmegapu microprocessor.

First check the initial factory fuse settings with avrdude. This is needed because the Atmega48 initially runs at 1MHz and is therefore to slow for the programmer. Values other than 8. As you can see the low fuse byte has a hexadecimal value of 62 which in binary is , this is the initial factory setting as shown in Table Bit no. The initial clock source ist the internal RC oscillator set at 8. Bits 5 and 4 SUT 1, 0 select the start-up time of the chip.

The initial value of corresponds to the calibrated internal RC oscillator see Table , p. We just need to change the fuse low byte value from to , or from 0x62 to 0xE2 in hexadecimal. This is the command line statement: avrdude -c usbasp -p m48 -B 8 -v -v -v -v -U lfuse:w:0xe2:m -U lfuse:w:0xe2:m tells avrdude to write 0xe2 to the fuse low byte.

When you run this you should get text feedback in the command line window. Now try to read the fuses again: avrdude -B 8. As an example lets take a 16MHz crystal, according to Table , p. Low power crystal oscillator 2.

Full swing crytal oscillator In my case I want to use the Atmega48 with an external PSU so I need not worry about power consumption so I will choose the second setting. The frequency range is 0.

The command line statement fort hat is: avrdude -c usbasp -p m48 -B 8 -v -v -v -v -U lfuse:w:0xF7:m From now on the Atmega48 will be using the external crystal oscillator to run at 16MHz.

If needed you can always reprogram the chip to run at other frequencies. Binary Hex precede with 0x 0.

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ATMEGA48-20PU

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. Depending on the clock selection fuse settings, PB6 can be used as input to the inverting Oscil- lator amplifier and input to the internal clock operating circuit. Depending on the clock selection fuse settings, PB7 can be used as output from the inverting Oscillator amplifier. The PC As inputs, Port C pins that are externally pulled low will source current if the pull-up resistors are activated.

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Программирование ATmega48-20PU

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