ST10 with external RAM

[ashley2]

Posted on November 22, 2007 at 22:26

ST10 with external RAM

[ashley2]

Posted on November 22, 2007 at 20:36

Hi all,

I am trying to interface an ST10F269 to external RAM (located inside a spartan FPGA). I would like to memory map my ram in the empty space between 0x8000 and 0x9FFF. Unfortunately no matter how hard I try I cant seem to get external memory access to work to that location. With the startup file attached used, I set BUSCON2 to enable the external bus, and address to 0x8000, range 8k.

Here is the funny thing, out of desperation I went through every memory location while scoping the external bus to see when an access was being made. It turns out that external access is being made when I address the ranges 0xA800-0xAFFF and 0xE800-0xEFFF. Now the later address makes sense as that is the CAN and RTC peripherals that are not enabled, so addressing them results in external memory bus access. But the 0xA800-0xAFFF range doesn't make sense.

Anyways, there is still no external bus access in the 0x8000-0x9FFF range like I want...

Any help would be greatly appreciated as I am out of ideas!

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Attachments :

START167.A66 : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I09f&d=%2Fa%2F0X0000000bXv%2FBW0zI48_i7wYUZ5YzNFNRRxE215Gk85wjJTzNCgX6T4&asPdf=false

[ashley2]

Posted on November 22, 2007 at 20:45

D'oh, sorry I attached a startup file I had been playing with, this is the correct one...

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Attachments :

START167.A66 : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I0DA&d=%2Fa%2F0X0000000bXr%2FGNT2nWynZ7ZLxo.sDEUzm.DeQvAaFYhc6rBDrenYWCA&asPdf=false

[ashley2]

Posted on November 22, 2007 at 22:26

Update: When I disable XRAM2 which is normally mapped between 0xc000 and 0xDFFF i can now externally address the above ranges as well as 0xC000-0xDFFF and 0x8000-0x9FFF. Unfortunately that doesn't solve my problem as I need to use the XRAM2 block. It does not seem to make any difference what I set the ADDSRESL registers to, as long as the BUSACT bit is set the four address ranges can be externally accessed!

I am now even more stuck!