| Embedded Target for Motorola MPC555 | |
Downloading Boot and Application Code
RAM vs. Flash Memory
The Embedded Target for Motorola MPC555 (real-time target) writes a file containing the application executable code that must be programmed onto the MPC555. It also writes a file of symbolic information suitable for use with a debugger. The files are written to your working directory.
The format of the code and symbol files depends on your selection from the Target memory model menu in the MPC555-DK (real-time) options category of the Real-Time Workshop pane, as follows:
FLASH option, files in a format suitable for downloading into on-chip flash memory are generated. The naming convention for these files is model_flash.bin (code only), and model_flash.out (debugging symbols). You can download code to flash memory via the CAN bus, or via the MPC555's BDM port.
RAM option, files in a format suitable for downloading into RAM are generated. The naming convention for these files is model_ram.srec (code only), and model_ram.out (code plus debugging symbols). You can download code to RAM via the CAN bus, or via the MPC555's BDM port.
There are advantages and disadvantages to each memory model.
Loading the application code into RAM is faster than loading it into flash memory. In addition, by using RAM you can avoid using up the programming cycles of the flash memory; this lengthens the usable lifetime of the flash memory. Running the application from RAM is a good option for initial testing of the application.
To program applications into RAM, your target hardware must have additional RAM external to the MPC555 on-chip RAM. The Embedded Target for Motorola MPC555 does not support downloading of code to the MPC555 on-chip RAM, because the MPC555 has only 26K of on-chip RAM.
For final deployment, or to load code onto a test board for use at a test site, you will generally want to program your code into the nonvolatile flash memory. 416K of flash memory is available for application code. Code programmed into flash memory is persistent and restarts when the board is powered on.
To download code to flash memory, you must first load a binary boot code file into the flash memory. The Embedded Target for Motorola MPC555 provides the boot code file. You must load the boot code into flash memory in order to run application code from flash memory; the boot code is also required if you want to program the MPC555 via CAN.
To understand the download process, it is first necessary to review the memory organization on the MPC555 and the operation of the boot code. This is described in Overview of Memory Organization and the Boot Process. If you just want to get started without reading about how the process works, you can jump ahead to the section Downloading Boot Code.
| | Downloading the Application to RAM via CAN | Overview of Memory Organization and the Boot Process | |