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# (for DDR) file: u-boot/cpu/mips/ar7240/meminit.c # (for PLL) file: u-boot/board/ar7240/common/lowlevel_init.S # this settings are taken from source of u-boot for this board After that we need use the program for JTAG and we have access to the flash chip. Depress the button (manual nTRST) - in this case the router or the AR7241 processor will be in TAP modeĦ. Press and hold the button (manual nTRST)Ĥ. Connect the JTAG cable to Router and PCģ.
#Jtag to debrick router manual
In practical use was discovered that the router MR3220v1.2 (AR7241) is still possible to use and JTAG interface and the SPI Flash Chip via JTAG interface as follows:Īfter pre-connecting to the router Simply DLC5 JTAG cable (this cable is only used: TDI, TDO, TMS, TCK pins) I made a manual nTRST switch, by soldering the Button between the CS# and VCC line (between this lines need to use resistor 10…50 ohms).Ģ.
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More information about the EJTAG specification can be found at this link. As You can understand it is critical for SPI flash-chip that needs CS#. Simply Wiggler JTAG cable used nTRST always pulled to the VCC for logical "1" (after the initialization of the cable) - it is usually necessary to confirm the MIPS EJTAG specification. When using the EJTAG on the router, usually nTRST (negative TAP Reset) is connected to VCC line – this way enabled TAP controller. on one pin is located nTRST, CS# and GPIO. Oxblogs tests didnt get the old router up and running at 100, but the basic idea is worth a shot if you have a bricked router sitting around. On processors AR7241 and AR7242 (Critical for the routers with SPI Flash Memory) was changed the location of the CS# for Flash Chip (compared with an AR7240, where CS#-pin = 75-pin) and designated as a 80-pin = CS# - i.e. RST - also disables the JTAG, ie full chip reset (same as off/on the router). Unlike nSRST which resets the CPU but JTAG is still active. If on PCB board of the router no place to EJTAG, then it is usually nTRST, TDI, TDO, TMS, TCK pins is used as a GPIOs pins.īut RST (nSRST) pin is always connected to the VCC line (usually via a resistor) and is also a GPIO-pin.