SmartDesign MSS
SPI Configuration
User Guide
Introduction
The SmartFusion Microcontroller Subsystem (MSS) provides two SPI hard peripherals (APB_0 and APB_1 sub busses) with optional FPGA fabric slave select ports extension.
The actual behavior of each SPI instance must be defined at the application level using the SmartFusion MSS SPI Driver provided by Actel.
In this document, we describe how you can enable the MSS SPI instances and access the fabric slave select ports. For more details about the MSS SPI hard peripherals, please refer to the Actel SmartFusion Microcontroller Subsystem User’s Guide.
Configuration Options
Enabling/Disabling SPI Instances. On the MSS canvas, you need to enable (default) or disable each SPI instance based on whether it is being used in your current application. Disabled SPI instances are held in reset (lowest power state) after the Actel system boot code is executed. Enabled SPI instances external ports – MSS I/Os – are also automatically configured by the Actel system boot code. Note that MSS I/Os allocated to a SPI instance are available to connect to MSS GPIOs if that SPI instance is disabled. Refer to the MSS GPIO configurator handbook for more details.
Fabric Slave Select Extension. You may drive up to 3 slave select signals for SPI_0 and 7 for SPI_1 into the FPGA fabric; to do this, you need to manually promote to the top level the FAB_SS[] port present on the MSS SPI instance(s) used in your application. You can then use the FAB_SS port in the next level of hierarchy where it can be ‘sliced’ as individual slave select signals.
Port Description
| Port Name | Port Group | Direction | PAD? | Description |
| DI | PADs | In | Yes | Shift data in (master or slave) |
| DO | PADs | Out | Yes | Serial data out (generated by SPI as master) |
| CLK | PADs | Inout | Yes | Shift clock out (generated by SPI as master) |
| SS | PADs | Inout | Yes | External dedicated slave select port (generated by SPI as master) |
| FAB_SS[n:1] | Out | No | Optional routed slave select ports (generated by SPI as master) |
Notes:
- PAD ports are automatically promoted to top throughout the design hierarchy.
- Non-PAD ports must be promoted manually to the top level from the MSS configurator canvas to be available as the next level of hierarchy.
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Documents / Resources
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Actel SmartDesign MSS SPI Configuration [pdf] User Guide SmartDesign MSS SPI Configuration, SmartDesign MSS, SPI Configuration, Configuration |
