ARM Based SoC design Tutorial : Practical 1.
-Aviral Mittal.
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Section 2
This Section describes the ARM's AHB Multilayered Bus Matrix RTL generation:
This component is a multilayered AHB bus which is used to connect the processor to the memories. Actually the bus matrix is connected to AHB2SRAM designs, before the memories, and the memories are then connected to AHB2SRAM designs.
The AHB2SRAM designs convert the AHB protocol signals to SRAM signals.

The ARM's Multilayered Bus Matrix IP is present in the following directory: (This directory would have been created by the user following the download of the ARM Design Start Eval Cortex-M3 processor Kit from ARM's website, as described in the previous section).
AT421-MN-80001-r0p0-02rel0/cmsdk/logical/cmsdk_ahb_busmatrix
This directory has 3 following directories:
bin
verilog
xml

The RTL generation is done by providing the specification for the matrix using a configuration xml file. This configuration xml file must be present in the 'xml' directory. By default ARM provides some example configuration files  The configuration xml file for this tutorial has been prepared for the user to analyze it.

The specification of the matrix includes the following:
The XML config file is briefly described in the figure below:






Once the configuration is specified, the script 'BuildBusMatrix.pl' is used to generate the Bus Matrix RTL. Full command syntax is also provided. Keep reading.


The 'cmsdk_ahb_busmatrix' component supports up-to 15 Masters and 15 Slave.
In this tutorial this IP is configured to use 5 Slave Ports (to which the system masters would connect to) and 4 Master Ports (to which the system Slaves will connect to). Remember as per the AHB protocol, the AHB protocol signals are asymmetric, i.e. a Master connects to a Slave and a Slave connects to a Master. Throughout this tutorial/course this has to be kept in mind.

The following figure provides the specification of the Bus Matrix we intend to built RTL for:





The figure above is quite self-explanatory:

While the above describes the connectivity, the following describes the System Slave address regions.


Yes, there is no System Master M2 (and corresponding S2 port on Bus Matrix) and the order of System Slaves isn't in increasing order (going from left to right, S3 comes before S2), but this doesn't matter, and there isn't any technical reason behind this naming.

Things to Note:

To configure the ARM's bus matrix to the above specification, the 'xml' spec file, described above is needed.
An example 'xml' file is provided in the following directory by ARM:
AT421-MN-80001-r0p0-02rel0/cmsdk/logical/cmsdk_ahb_busmatrix
We take the example xml configuration file and configure it to the above spec to get this.
When you click on line above, you will see the contents of an xml file.
Copy+Paste it into a file and name it 'cortexm3_soc.xml'. Note: Remember to name the file as '.xml', when you click on above link the file is shown as .txt.

Save the above as 'cortexm3_soc.xml' in the 'xml' directory.
Now issue the following command from the directory:
AT421-MN-80001-r0p0-02rel0/cmsdk/logical/cmsdk_ahb_busmatrix
./bin/BuildBusMatrix.pl -xmldir xml -cfg cortexm3_soc.xml -over 
This may give you the following error:
"Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/}{ <-- HERE ([a-z0-9\.\-\_]+)\[1\]$/ at bin/lib/xmlparser.pm line 852."
If (and only if) you get this error, then open the file
'bin/lib/xmlparser.pm' and edit line number 852 as shown below:
if (  =~ s/}{([a-z0-9\.\-\_]+)\[1\]$// ) {  = ; }
if ( =~ s/\}\{([a-z0-9\.\-\_]+)\[1\]$// ) { = ; }
All you have to do is, put a backslash '\' before the '}' and '{' characters as shown above.
Save the file and try the build command again.

./bin/BuildBusMatrix.pl -xmldir xml -cfg cortexm3_soc.xml -over

This will generate the Bus-Matrix RTL for the above spec.
The RTL will be present tin the following directory:
AT421-MN-80001-r0p0-02rel0/cmsdk/logical/cmsdk_ahb_busmatrix/verilog/built
Copy the following RTL files from the above directory to the directory:
'asic_design/xilinx/cortexm3_soc/cm3_matrix/rtl'
You may have to create this directory:
cm3_in.v
cm3_matrix.v
cm3_matrix_default_slave.v
cm3_matrix_lite.v
cm3_outM0.v
cm3_outM1.v
cm3_outM2.v
cm3_outM3.v
cmsdk_MyArbiterNameM0.v
cmsdk_MyArbiterNameM1.v
cmsdk_MyArbiterNameM2.v
cmsdk_MyArbiterNameM3.v
cmsdk_MyDecoderNameS0.v
cmsdk_MyDecoderNameS1.v
cmsdk_MyDecoderNameS3.v
cmsdk_MyDecoderNameS4.v
cmsdk_MyDecoderNameS5.v

Note: The file 'cm3_matrix_lite.v' contains the TOP level for the Bus Matrix.



All the components needed to create the first SoC RTL are now ready to be used.
Next these components will be 'connected' together to build the Stage 1 SoC RTL.

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