3.1 Loading
A program needs to be placed into the target device's memory before it may be executed. Loading is the process of preparing a program for execution by initializing device memory with the program's code and data. A loader might be another program on the device, an external agent (for example, a debugger), or the device might initialize itself after power-on, which is known as bootstrap loading, or bootloading.
The loader is responsible for constructing the load image in memory before the program starts. The load image is the program's code and data in memory before execution. What exactly constitutes loading depends on the environment, such as whether an operating system is present. This section describes several loading schemes for bare-metal devices. This section is not exhaustive.
A program may be loaded in the following ways:
- A debugger running on a connected host workstation. In a typical embedded development setup, the device is subordinate to a host running a debugger such as Code Composer Studio (CCS). The device is connected with a communication channel such as a JTAG interface. CCS reads the program and writes the load image directly to target memory through the communications interface.
- "Burning" the load image onto an EPROM module.The hex converter (hex430) can assist with this by converting the executable object file into a format suitable for input to an EPROM programmer. The EPROM is placed onto the device itself and becomes a part of the device's memory. See Section 12 for details.
- Bootstrap loading from a dedicated peripheral, such as an I2C peripheral. The device may require a small program called a bootloader to perform the loading from the peripheral. The hex converter can assist in creating a bootloader.
- Another program running on the device. The running program can create the load image and transfer control to the loaded program. If an operating system is present, it may have the ability to load and run programs.