1. Stacking: Stack two VSX boards together through the PC104 interface.

2. BoR: BoR (bridge of redundancy), which is a set of buses designed by our company for fault tolerance. The two ends of the bus are connected to the fault-tolerant interface (Redundancy) of two motherboards (A, B).

3. COM9: There is also a com9 on my company's board. In the BIOS: Chipset → Southbridge Configuration → Redundancy Control Configuration, set the port address and interrupt number. COM9 can be used as the comparison between the two system information and keep the master and slave board. Card information synchronization, of course, you can also use com9 as a high-speed serial port for the transfer of any information between the two cards.

as the picture shows:

4. Controllable and Uncontrollable

The so-called controllable I/O means that the same I/O is used by both devices. The host computer has control I/O rights for the working machine, and it only follows the host to run and does not participate in control.

The commonly used controllable I/Os are: serial port, parallel port, GPIO, keyboard mouse.

Uncontrolled I/O: USB, Ethernet, LCD ...

six. Fault Tolerance Test

1. For the test of register address 6DH, judge whether the system is Master or Slave by reading the data of register address 6DH. You can use software to read the value of 6DH (00000010 master master, 00000001 slave slave) to determine the master slave master board.

as the picture shows:

2. Determine the master/slave drive by reading/writing the SRAM address value in debug mode. The Master system can access the SRAM space of the Slave system. The access (read/write) mode can be set in the BIOS. SLAVE The system cannot access the master system's SRAM. Because Master has mastership and Slave does not.

Seven. Typical case analysis

The above picture shows a ground division of the aviation division. When the host is powered on, two VSX-6154 motherboards are started at the same time. One random master and one slave are determined in chronological order. Master has mastership and suppresses Slave's various functions, so the display shows Master's content. Slave just follows the Master. The mastert receives the information and transmits the information to the display. At the same time, the information matching with the slave is completed through the BoR bus to achieve the synchronization of the information. If the Master restarts because of an accident, then the Master pushes control to the Slave at the moment of crash, Slave becomes the Master after receiving the Master's signal, and will continue to run. After the original Master lost control power by restarting or repairing, it became the new Slave until the machine took over the work of the Master again.