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AR# 23804

8.1i EDK - Design fails when the block RAM memory is greater than 64 KB on Virtex-4

Description

My design fails when I create a block RAM memory structure in XPS that is greater than 64 KB.

Solution

XPS is taking advantage of the cascaded block RAM feature in Virtex-4. However, Platgen creates the memory structure such that the "UPPER" memory becomes filled with the software application before the "LOWER" memory does.

To work around this problem:

1. Run "Create Netlist" in XPS.

2. Modify the memory structure of the ".bmm" file that was created in the project's implementation directory from:

// File: C:\test_project\128k\mytest_ml401_128K\implementation\system.bmm

ADDRESS_MAP microblaze_0 MICROBLAZE 100

ADDRESS_SPACE lmb_bram_combined COMBINED [0x00000000:0x0001ffff]

ADDRESS_RANGE RAMB16

BUS_BLOCK

lmb_bram/lmb_bram/ramb16_0 [31:31] ;

lmb_bram/lmb_bram/ramb16_1 [30:30] ;

:

:

lmb_bram/lmb_bram/ramb16_30 [1:1] ;

lmb_bram/lmb_bram/ramb16_31 [0:0] ;

END_BUS_BLOCK;

BUS_BLOCK

lmb_bram/lmb_bram/ramb16_32 [31:31] ;

lmb_bram/lmb_bram/ramb16_33 [30:30] ;

:

:

lmb_bram/lmb_bram/ramb16_62 [1:1] ;

lmb_bram/lmb_bram/ramb16_63 [0:0] ;

END_BUS_BLOCK;

END_ADDRESS_RANGE;

END_ADDRESS_SPACE;

END_ADDRESS_MAP;

to:

// File: C:\test_project\128k\mytest_ml401_128K\implementation\system.bmm

ADDRESS_MAP microblaze_0 MICROBLAZE 100

ADDRESS_SPACE lmb_bram_combined COMBINED [0x00000000:0x0001ffff]

ADDRESS_RANGE RAMB16

BUS_BLOCK

lmb_bram/lmb_bram/ramb16_32 [31:31] ;

lmb_bram/lmb_bram/ramb16_33 [30:30] ;

:

:

lmb_bram/lmb_bram/ramb16_62 [1:1] ;

lmb_bram/lmb_bram/ramb16_63 [0:0] ;

END_BUS_BLOCK;

BUS_BLOCK

lmb_bram/lmb_bram/ramb16_0 [31:31] ;

lmb_bram/lmb_bram/ramb16_1 [30:30] ;

:

:

lmb_bram/lmb_bram/ramb16_30 [1:1] ;

lmb_bram/lmb_bram/ramb16_31 [0:0] ;

END_BUS_BLOCK;

END_ADDRESS_RANGE;

END_ADDRESS_SPACE;

END_ADDRESS_MAP;

3. Look in the logfile when the netlist was created and rerun NGDBuild from the command line, as was run in the logfile, making sure to include the newly modified ".bmm" file.

4. You can now run "Create Bitstream" in XPS.

These problems have been fixed in the latest EDK 8.2i Service Pack, available at:

http://www.xilinx.com/xlnx/xil_sw_updates_home.jsp
The first service pack containing the fix is EDK 8.2i Service Pack 2.

AR# 23804
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article