An Important Note Regarding the Crystal Frequency

Both the MAVRIC and the M128 REV B boards incorporate an Atmel ATmega128 MCU which is designed for a maximum operating frequency of 16 MHz. This makes the ATmega128 very attractive for its high speed operation.

However, there is one advantage to clocking the ATmega128 MCU a little slower (aside from using less power), and that is so that it can generate error free baud rates all the way up to 230.4 kbps. The magic frequency for this is 14.7456 MHz. But using this lower frequency results in a 7.8% reduction in the clock speed from 16 MHz, and thus, a 7.8% potential reduction in the speed with which it can run your programs.

Note however, that at the 3 highest baud rates (250kbps, 500kbps, and 1Mbps), the 16 MHz crystal produces error free baud rates, while the 14.7456 MHz crystal does not.

The following table illustrates the %error in the baud rates at 16 MHz and at 14.7456 MHz. These numbers come directly from the Atmel datasheet for the ATmega128:

Since generating perfect baud rates is a somewhat specialized requirement, by default, your Kit or Assembled and Tested board will include a 16 MHz crystal - the maximum frequency guaranteed to work reliably, delivering the most speed and power to your application.

However, each application has its own special needs, and no one crystal frequency will be right choice for everyone. Therefore, a 14.7456 MHz option is available when you place your order. Just choose the desired crystal frequency from the drop-down option list near the "Add to Cart" button for that item.