Dual-core CPU build Reset System

During the construction of a dual-core processor, the system usually requires mutual control between the dual-core. If there is such an application: one of the two CPUs is cpu_master, and the other is cpu_slave, cpu_mater needs to control the cpu_slave program to run, only cpu_mater must be available during power-on, and cpu_slave must be in the reset State. To achieve this mechanism, you must introduce the cpu_slave reset pin and then use it for control, however, by default, the reset pins of the two CPUs in the dual-core system are connected together. Therefore, you need to set the reset pin of cpu_slave in the software, as shown in:

Double-click cpu_slave. Then, a dialog box is displayed, and the following page is displayed.

After the system is built, we can see that there is a system reset and a cpu_slave reset pin.

To test whether the dual-core build is successful, connect the two reset pins, and then download the test code for the two CPUs.

The cpu_master test is successful. You can run it after downloading it to the CPU.

Now we test cpu_slave. However, after a test program is downloaded to cpu_slave, the following error occurs:

The prompt shows that the _ start () function is not found. This is the function in the system startup code. Why can't I find it? I was puzzled. Later, I asked Junge to know that the CPU reset pin actively introduced by the system on the system chip was a high-level reset. Therefore, a non-door must be added at the front end of the reset pin. As shown in:

After resetting, perform the test again. Everything is normal. Why did the previous error occur when the door was not added? Because the CPU kernel is actually a high-level reset, at that time, cpu_slave was always in the reset state, and no address jump was made, so when the system started the address, the CPU did not jump to _ start () in the function area, the software prompts that the _ start () function cannot be found. You can run the program one step further. No matter how one step is run, the program is always in the first instruction, that is, the place where the reset address is located, such:

This is a little experience. Pay attention to the reset pin connection method when using it in the future. If no reset pin is introduced in the inner part of the Nios dual core, that is, the system can be reset directly, then there will be no such problem.