ATBIOS

Introduction
The ATBIOS is an ATmega644P running at 16MHz that utilizes the ATBIOS firmware. It is responsible for all the pre-load "BIOS" functionality of the system. This includes the POST sequence and all configuration functionality of the BIOS.

Control and Connection
The ATBIOS is connected to the system via the SPI bus and manages its own SPI-based FLASH configuration RAM. This SPI FLASH IC is where all the BIOS configuration is kept. The SPI FLASH is an 8-pin W25X or other compatible/similar IC.

System Voltage
There are two analog inputs into the ATBIOS whereby the ATBIOS can determine voltage and current. The current sensing resistors are found in the power supply blueprint. The ATBIOS acts as a watch dog on the voltage and will bring the system down "gracefully" if it determines there is not enough voltage/current to handle it.

AMPS Reset
The ATBIOS has direct lines to the !RESET pins of each MCU in the AMPS bundle. The ATBIOS, upon first booting, holds the microcontroller CPUs in reset until clock and voltage has settled, then releases the lines and lets the AMPS boot the rest of the way up.