Книга: Embedded Linux Primer: A Practical, Real-World Approach

14.4.1. Programming Flash Using a JTAG Probe

14.4.1. Programming Flash Using a JTAG Probe

Many hardware probes include the capability to program a wide variety of Flash memory chips. The Abatron BDI-2000 is no exception. The BDI-2000 configuration file includes a [FLASH] section to define the characteristics of the target Flash. Refer to Appendix F for a sample. The [FLASH] section defines attributes of the Flash chip as used in a particular design, such as the chip type, the size of the device, and its data bus width. Also defined are the location in memory and some way to describe the chip's storage organization.

When updating one portion of the Flash, you often want to preserve the contents of other portions of the same Flash. In this case, your hardware probe must have some way to limit the sectors that are erased. In the case of the Abatron unit, this is done by adding a line starting with the keyword ERASE for each sector to be erased. When the erase command is issued to the Abatron unit via its telnet user interface, all sectors defined with an ERASE specification are erased. Listing 14-20 demonstrates erasing a portion of Flash on a target board and subsequently programming a new U-Boot bootloader image.

Listing 14-20. Erase and Program Flash

$ telnet bdi
Trying 192.168.1.129...
Connected to bdi (192.168.1.129).
Escape character is '^]'.
BDI Debugger for Embedded PowerPC
=================================
... (large volume of help text)
uei> erase
Erasing flash at 0xfff00000
Erasing flash at 0xfff10000
Erasing flash at 0xfff20000
Erasing flash at 0xfff30000
Erasing flash at 0xfff40000
Erasing flash passed
uei> prog 0xfff00000 u-boot.bin BIN
Programming u-boot.bin, please wait ....
Programming flash passed
uei>

First we establish a telnet session to the Abatron BDI-2000. After some initialization, we are presented with a command prompt. When the erase command is issued, the Abatron displays a line of output for each section defined in the configuration file. With the configuration shown in Appendix F, we defined five erase sectors. This reserves up to 256KB of space for the U-Boot bootloader binary.

The prog command is shown with all three of its optional parameters. These specify the location in memory where the new image is to be loaded, the name of the image file, and the format of the filein this case, a binary file. You can specify these parameters in the BDI-2000 configuration file. In this case, the command reduces to simply prog without parameters.

This example only scratches the surface of these two BDI-2000 commands. Many more combinations of usage and capabilities are supported. Each hardware JTAG probe has its own way to specify Flash erasure and programming capabilities. Consult the documentation for your particular device for the specifics.

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