Anastasia Klimchuk has uploaded this change for review. ( https://review.coreboot.org/c/flashrom/+/83451?usp=email )
Change subject: doc: Add doc for in-system programming ......................................................................
doc: Add doc for in-system programming
The page on wiki is here: https://wiki.flashrom.org/ISP
Change-Id: If4752f0f02ae973b3d832f42166de643d95c9f97 Signed-off-by: Anastasia Klimchuk aklm@flashrom.org --- A doc/user_docs/1200px-DIP_socket_as_SOIC_clip.jpg A doc/user_docs/Pomona_5250_soic8.jpg A doc/user_docs/in_system.rst M doc/user_docs/index.rst 4 files changed, 46 insertions(+), 0 deletions(-)
git pull ssh://review.coreboot.org:29418/flashrom refs/changes/51/83451/1
diff --git a/doc/user_docs/1200px-DIP_socket_as_SOIC_clip.jpg b/doc/user_docs/1200px-DIP_socket_as_SOIC_clip.jpg new file mode 100644 index 0000000..c3db692 --- /dev/null +++ b/doc/user_docs/1200px-DIP_socket_as_SOIC_clip.jpg Binary files differ diff --git a/doc/user_docs/Pomona_5250_soic8.jpg b/doc/user_docs/Pomona_5250_soic8.jpg new file mode 100644 index 0000000..83f8c3e --- /dev/null +++ b/doc/user_docs/Pomona_5250_soic8.jpg Binary files differ diff --git a/doc/user_docs/in_system.rst b/doc/user_docs/in_system.rst new file mode 100644 index 0000000..84716d3 --- /dev/null +++ b/doc/user_docs/in_system.rst @@ -0,0 +1,45 @@ +===================== +In-System Programming +===================== + +**In-System Programming** (ISP) sometimes also called **in situ programming** is used to describe +the procedure of writing a flash chip while it is (already/still) attached to the circuit +it is to be used with. Of course any normal "BIOS flash" procedure is a kind of ISP +but when we refer to ISP we usually mean something different: programming a flash chip by external means +while it is mounted on a motherboard. + +This is usually done with SPI chips only. Some mainboards have a special header for this +(often named "ISP", "ISP1", or "SPI") and there should be no problem with accessing the chip +then as long as the wires are not too long. + +If there is no special header then using a special SO(IC) clip is an easy and reliable way +to attach an external programmer. They are produced by different vendors (e.g. Pomona, 3M) +and are available from many distributors (e.g. Distrelec) for 20-50$/€. + +Problems +======== + +* Check the other potential problems (:doc:`misc_notes`) with other types of programming setups first. +* The SPI bus is not isolated enough. Often parts of the chipset are powered on partially + (by the voltage supplied via the Vcc pin of the flash chip). In that case + disconnect Vcc from the programmer and power it with its normal PSU and: + + * Try powering up the board normally and holding it in reset (e.g. use a jumper instead of the reset push button). + * Some chipsets (e.g. Intel ICHs/PCHs) have edge triggered resets. In this case holding them in reset will not work. + This is especially a problem with Intel chipsets because they contain an EC (named ME by Intel, see :doc:`management_engine`), + which uses the flash (r/w!). In this case you can trigger the reset line in short intervals. + For example by connecting it to the chip select (CS) line of the SPI bus or a dedicated clock signal from the programmer. + This should not be too fast though! Reset lines usually require pulses with a minimum duration. + * On some boards, you can try disconnecting the ATX12V header (yellow/black wires only) from the motherboard, + or even remove the CPU or RAM - if the programmer supports SPI sniffing, you may be able to verify that the there is no SPI traffic. + +Images +======== + +Pomona 8-pin SOIC clip with attached jumper wires. + +.. image:: Pomona_5250_soic8.jpg + +A cheap, but very fragile alternative: DIP socket as clip + +.. image:: 1200px-DIP_socket_as_SOIC_clip.jpg diff --git a/doc/user_docs/index.rst b/doc/user_docs/index.rst index 960659e..3ca928a 100644 --- a/doc/user_docs/index.rst +++ b/doc/user_docs/index.rst @@ -9,4 +9,5 @@ chromebooks management_engine misc_intel + in_system misc_notes
-
Anastasia Klimchuk (Code Review)