| xPC Target | |
Real-Time Kernel
xPC Target does not require DOS, Windows, Linux, or any another operating system on the target PC. Instead, you boot the target PC with a boot disk that includes the highly optimized xPC Target kernel.
However, the xPC Target Embedded Option requires DOS and a DOS license at boot time. For more information, see the xPC Target User Guide documentation.
Target boot disk -- The boot disk eliminates the need to install software, modify existing software configurations, or access the hard disk on the target PC. This arrangement allows you to use the target PC for testing real-time applications, and then when you are finished with your tests, you can use the target PC again as a desktop computer. Software is not permanently installed on the target PC unless you are deliberately using the xPC Target Embedded Option and install a stand-alone application on the hard disk or flash memory.
Target PC BIOS -- Selecting a newer BIOS allows you to customize settings for better control over the real-time behavior of the system. For example, you can suppress checking for a keyboard, and switch off any power save features.
The xPC Target kernel runs only on a PC compatible system and a key component of every PC compatible system is the BIOS. The BIOS is the only software component which is needed by the xPC Target kernel.
After the BIOS is loaded, it searches the target boot disk for a bootable image (executable). This bootable image includes a 16-bit part and a 32-bit part. The 16-bit part runs first because the CPU is still in real mode. It prepares the descriptor tables and in addition to other things switches the CPU to protected mode. Next, the 32-bit part runs. It prepares the target PC environment for running the kernel and finally starts the kernel.
After loading the kernel, the target PC does not make calls to the BIOS or DOS functions. The resources (for example, interrupt controller, UART, and counters) on the CPU motherboard are addressed entirely through I/O addresses.
Real-time kernel -- After the kernel starts running, it displays a welcome message with information about the host-target connection. The kernel activates the application loader and waits to download a target application from the host PC. The loader receives the code, copies the different code sections to their designated addresses, and sets the target application ready to start. You can now use xPC Target functions and other utilities to communicate with the target application.
It is important to note, that after the CPU switches to protected mode (32-bit), none of the xPC Target components switch the CPU back to real mode (16-bit).
The generated real-time application and the real-time kernel are compiled as Windows NT applications with a flat memory model. This provides full 32-bit power without time consuming 16-bit segment switching and DOS extenders.
Target PC heap -- The initialization code of the target application reserves the remaining unused RAM as heap. The memory available for the heap is displayed on the left side of the target screen as Memory. By default, it is 4 MB less than the entire RAM installed (1 MB for the application; 3 MB for the kernel). Normally, the largest part of the heap is used by signal logging because logging acquires and stores data during the entire run.
You can define the amount of memory available for data logging in the Simulation Parameters dialog box. See Entering the Real-Time Workshop Parameters.
| | Features of xPC Target | Real-Time Application | |