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The custom functions subsystem can be used to implement application-specific user-defined co-processors
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The custom functions subsystem can be used to implement application-specific user-defined co-processors
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(like encryption or arithmetic accelerators) or peripheral/communication interfaces. In contrast to connecting
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(like encryption or arithmetic accelerators) or peripheral/communication interfaces. In contrast to connecting
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custom hardware accelerators via the external memory interface, the CFS provide a convenient and low-latency
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custom hardware accelerators via the external memory interface, the CFS provide a convenient and low-latency
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extension and customization option.
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extension and customization option.
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The CFS provides up to 32x 32-bit memory-mapped registers (see register map table below). The actual
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The CFS provides up to 32x 32-bit memory-mapped registers `REG` (see register map table below). The actual
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functionality of these register has to be defined by the hardware designer.
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functionality of these register has to be defined by the hardware designer.
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[INFO]
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[INFO]
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Take a look at the template CFS VHDL source file (`rtl/core/neorv32_cfs.vhd`). The file is highly
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Take a look at the template CFS VHDL source file (`rtl/core/neorv32_cfs.vhd`). The file is highly
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commented to illustrate all aspects that are relevant for implementing custom CFS-based co-processor designs.
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commented to illustrate all aspects that are relevant for implementing custom CFS-based co-processor designs.
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register map table below). Note that all interface registers provide 32-bit access data of type `uint32_t`.
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register map table below). Note that all interface registers provide 32-bit access data of type `uint32_t`.
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[source,c]
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[source,c]
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----
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----
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// C-code CFS usage example
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// C-code CFS usage example
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CFS_REG_0 = (uint32_t)some_data_array(i); // write to CFS register 0
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NEORV32_CFS.REG[0] = (uint32_t)some_data_array(i); // write to CFS register 0
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uint32_t temp = CFS_REG_20; // read from CFS register 20
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uint32_t temp = NEORV32_CFS.REG[20]; // read from CFS register 20
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----
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----
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**CFS Interrupt**
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**CFS Interrupt**
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The CFS provides a single one-shot interrupt request signal mapped to the CPU's fast interrupt channel 1.
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The CFS provides a single one-shot interrupt request signal mapped to the CPU's fast interrupt channel 1.
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by the hardware designer. The size of the input signal conduit `cfs_in_i` is defined via the (top's) _IO_CFS_IN_SIZE_ configuration
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by the hardware designer. The size of the input signal conduit `cfs_in_i` is defined via the (top's) _IO_CFS_IN_SIZE_ configuration
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generic (default = 32-bit). The size of the output signal conduit `cfs_out_o` is defined via the (top's)
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generic (default = 32-bit). The size of the output signal conduit `cfs_out_o` is defined via the (top's)
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_IO_CFS_OUT_SIZE_ configuration generic (default = 32-bit). If the custom function subsystem is not implemented
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_IO_CFS_OUT_SIZE_ configuration generic (default = 32-bit). If the custom function subsystem is not implemented
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(_IO_CFS_EN_ = false) the `cfs_out_o` signal is tied to all-zero.
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(_IO_CFS_EN_ = false) the `cfs_out_o` signal is tied to all-zero.
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.CFS register map
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.CFS register map (`struct NEORV32_CFS`)
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[cols="^4,<5,^2,^3,<14"]
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[cols="^4,<5,^2,^3,<14"]
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[options="header",grid="all"]
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[options="header",grid="all"]
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|=======================
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|=======================
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| Address | Name [C] | Bit(s) | R/W | Function
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| Address | Name [C] | Bit(s) | R/W | Function
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| `0xfffffe00` | _CFS_REG_0_ |`31:0` | (r)/(w) | custom CFS interface register 0
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| `0xfffffe00` | `NEORV32_CFS.REG[0]` |`31:0` | (r)/(w) | custom CFS interface register 0
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| `0xfffffe04` | _CFS_REG_1_ |`31:0` | (r)/(w) | custom CFS interface register 1
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| `0xfffffe04` | `NEORV32_CFS.REG[1]` |`31:0` | (r)/(w) | custom CFS interface register 1
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| ... | ... |`31:0` | (r)/(w) | ...
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| ... | ... |`31:0` | (r)/(w) | ...
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| `0xfffffe78` | _CFS_REG_30_ |`31:0` | (r)/(w) | custom CFS interface register 30
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| `0xfffffe78` | `NEORV32_CFS.REG[30]` |`31:0` | (r)/(w) | custom CFS interface register 30
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| `0xfffffe7c` | _CFS_REG_31_ |`31:0` | (r)/(w) | custom CFS interface register 31
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| `0xfffffe7c` | `NEORV32_CFS.REG[31]` |`31:0` | (r)/(w) | custom CFS interface register 31
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|=======================
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|=======================
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