On Tuesday 02 June 2009 10:32:03 jie.zeng wrote: > On Tue, 2009-06-02 at 08:37 +0200, Michael Schwingen wrote: > > > I'm not sure. I thought that address must match the flash interface > > > specification. In this case, from the flash's datasheet where > > > descripted that. And also some other flash datasheet point the same > > > thing as below: Autoselect stage (cycle, addr, data) > > > Manfacturer ID(word) (1st, 555, AA) (2nd, 2AA, 55) (3rd, 555, 90) > > > Manfacturer ID(byte) (1st, AAA, AA) (2nd, 555, 55) (3rd, AAA, 90) > > > > > > Notice the address 0x2AA and 0x555, it's not 0x2aa * bus_width, but the > > > source code it is. Why? > > > > If you have multiple flashs wired up on 1 bus, then the address lines > > between CPU and flash are shifted, requiring correction. The addresses > > in the datasheet are *flash* addresses, not *CPU* addresses. > > In case flash_width == bus_width, they are the same. > > Maybe I got your word. Lets go on. > > If we want to access a register in the board, we must pass the base > address which tell cpu where the register reside and a proper > offset(depends on bus-width), right? If the offset is not fix the > datasheet, how the cpu can access that reg correctly? > > In my opinion, the base is 0x10000000 in this case. The offset(in fact > its on-chip addr) from datasheet(flash) are 0x2aa(word) and 0x555(byte). > So CPU write memory should use the address 0x100002AA or 0x10000555. But > now cpu use a wrong address which is 0x10000554. > > The result is that cannot get right ManufacturerID and probe failure. > > Regards >
As Michael tried to explain, you need to understand how your flash chip address bus is related to the cpu address bus. If you are writing from a 16 bit address bus to a 16bit flash chip the correspondence is 1-1 so address flash base+offset(0x2aa) will keep the same. On the contrary if the chip and cpu address width differs, you need to do a shift but _just_ on offset address. Please see pg 3 of cfi specification [0] for detailed info. 0x554 is also valid for 0x555. The former happens to be 0x2aa left shifted 1 bit. [0] http://www.jedec.org/download/search/jesd68-01.pdf -- Raúl Sánchez Siles Departamento de Montaje INFOGLOBAL, S. A. * C/ Virgilio, 2. Ciudad de la Imagen. 28223 Pozuelo de Alarcón (Madrid), España * T: +34 91 506 40 00 * F: +34 91 506 40 01 _______________________________________________ Openocd-development mailing list Openocd-development@lists.berlios.de https://lists.berlios.de/mailman/listinfo/openocd-development
