K64 External SRAM Question

[cuizhuangping]

Hello:

       Everyone, I am now using K64 as CPU core of my board. I Use an External SRAM (IS61LV51216) which have a size of 1M Byte as a supplement space of my board. However, I encountered a question  when I want to access upper 512k of the chip. I Map the whole 1M address to my internal address( 0x70000000-0x701000000). I can't access the address greater than 0x7008000. When I change the map address to( 0x70080000-0x701800000) , I can access the address(0x70080000-0x701000000) and can't access the remaining? Is there has any method to map to 1M external space?

      There, I have another question. Does the access speed of internal sram and external sram has great difference? When I use internal sram as my calculate variable,occupancy rate of cpu is 41%, which change to 97% when I defined my varible to external. Is there has any method to promote the external sram access speed?

[Hui_Ma]

Hi,

For the external SRAM is using Flexbus connected, please check the FB_CSMRn [BAM] bits setting.

For the external SRAM memory size is 1M Byte, the FB_CSMRn[BAM] bits value should be 0xF.

The Flexbus clock is using bus clock, which need to use 4 cycles to read 16/32 bit data.

If the external SRAM memory supports burst access, customer could set Flexbus to start burst transfer, which could enhance the external SRAM access speed.

Wish it helps.

best regards,

Ma Hui