Nios® V Processor Software Developer Handbook

ID 743810
Date 5/26/2023
Public

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4.2.3.2. Modifying Linker Memory Regions

If the default linker memory regions do not meet your needs, BSP Tcl commands let you modify the memory regions as you prefer.

Suppose you have a memory region named onchip_ram. The following Tcl script example separates the top 1024 bytes of onchip_ram to create a new region named onchip_special.

For more information about an explanation of each Tcl command used in this example, refer to the Board Support Package Tcl Commands .

# Get region information for onchip_ram memory region.
# Returned as a list.
set region_info [get_memory_region onchip_ram]

# Extract fields from region information list.
set region_name [lindex $region_info 0]
set slave_desc [lindex $region_info 1]
set offset [lindex $region_info 2]
set span [lindex $region_info 3]

# Remove the existing memory region.
delete_memory_region $region_name

# Compute memory ranges for replacement regions.
set split_span 1024
set new_span [expr $span-$split_span]
set split_offset [expr $offset+$new_span]

# Create two memory regions out of the original region.
add_memory_region onchip_ram $slave_desc $offset $new_span
add_memory_region onchip_special $slave_desc $split_offset $split_span

If you pass this Tcl script to niosv-bsp, it runs after the default Tcl script runs and sets up two memory regions named onchip_ram and onchip_special. Pass the Tcl script to niosv-bsp as follows:

When creating a new BSP:
niosv-bsp --create –-qsys=<Platform Designer system> --type=hal 
--script=reserve_1024_onchip_ram.tcl settings.bsp
When updating an existing BSP:
niosv-bsp --update --script=reserve_1024_onchip_ram.tcl settings.bsp

If you update your BSP without providing the --script option, your BSP reverts to the default linker memory regions and the onchip_special memory region disappears. To preserve it, please provide the --script option to your Tcl script.

For more information about using the --script argument, refer to the Calling a Custom BSP Tcl Script.