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Question about an external bus interface on MPC5674F

Question asked by YoungSeo LEE on Oct 31, 2017
Latest reply on Nov 1, 2017 by David Tosenovjan

i was implementing an external bus interface module to use an external SRAM, but was having problems accessing all areas of the external SRAM.


the memory map(MMU configuration) EBI(external bus interface) settings are as follows. 

TLB1 : 0x20000000 ~ 0x203FFFFF (4MB), CS0  => Allocation for 4MB external SRAM

TLB2:  0x20400000 ~ 0x205FFFFF (2MB), CS1

TLB3:  0x20600000 ~ 0x206FFFFF (1MB), Non-CS

TLB4:  0x20700000 ~ 0x207FFFFF (1MB), CS3


In the above configuration, i can only access 2MB area of the external SRAM(0x20000000 ~ 0x201FFFFF).

(If I access the 0x2020000 ~ 0x203fffff area, MOC5674F will shut down after a bus error is generated.)


why can not i access the rest of the external SRAM area(0x20200000 ~ 0x203FFFFF)?


Do I have to make additional settings besides the TLB setting and the EBI(chip select) setting? or am I only able to use 2MB due to a EBI constraints?