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Diffstat (limited to 'Documentation/flash_tutorial/no_ext_power.md')
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diff --git a/Documentation/flash_tutorial/no_ext_power.md b/Documentation/flash_tutorial/no_ext_power.md new file mode 100644 index 0000000000..b97ba4cc7a --- /dev/null +++ b/Documentation/flash_tutorial/no_ext_power.md @@ -0,0 +1,22 @@ +# Flashing firmware externally supplying no power + +On some mainboards the flash IC's Vcc pin is connected to the internal +power-rail, powering the entire board if the flash IC is powered externally. +Likely it powers other chips which access the flash IC, preventing the external +programmer from reading/writing the chip. It also violates the components' +power sequence, bringing the ICs into an undefined state. + +![][flash_ic_no_diode] + +Please have a look at the mainboard specific documentation for details. + +On those boards it's recommended to use a programmer without supplying power +externally. + +The key to read and write the flash IC is to put the machine into *S3* sleep- +state or *S5* sleep-state *maybe* with Wake-On-LAN enabled. +Another option that sometimes works is to keep the device in reset. This method requires +knowledge of the board schematics and might require hardware modifications. +Use a multimeter to make sure the flash IC is powered in those sleep states. + +[flash_ic_no_diode]: flash_ic_no_diode.svg |