The STM32F103 BluePill board serves as system controller, providing user-configurable clock and reset generator for MC6800, MC6850 transfer clock generator, periodic interrupt timer for the MC6800 and USB-to-UART bridge for ACIA. The computer is powered from PC via the USB cable.
At the PC side it appears as two VCOM ports: one for system controller configuration, another for ACIA communication.
The controller's firmware allows for setting the computer parameters: clock frequency of MC6800 and MC6850 (independently), SysTick timer period and optional PIA buffer directions. The settings may be stored in controller’s Flash. It may also reset the MC6800 or issue an NMI request to it based on a command entered from the terminal.
With proper BluePill firmware modifications, the board may support MC6802 in place of MC6800. This is the next step planned.