In RT PolarFire FPGA, the system service request is initiated by passing a 16-bit system service descriptor to the System Controller. The lower seven bits of the descriptor specify the service to be performed and the upper nine bits specify address offset. There is a 2 Kbytes internal mailbox RAM memory space. This space is used for passing the input data and storing the service request output that is returned by the System controller. The mailbox address specifies the service-specific data structure that is used for any additional inputs to or outputs from the service. On completion of service, the System Controller writes a status code indicating the successful completion of the system service or an error code. The following table lists the system service request descriptor bits. For information about mailbox read/write communication from Fabric, see UG0848 PolarFire System Services User Guide.
| System Service Descriptor Bit Field | Value | Description |
|---|---|---|
| 15:7 | MBOXADDR[10:2] | Specifies the address offset in mailbox RAM to access minimum four bytes of memory. Mailbox addresses are specified using a word offset (0-511). |
| 6:0 | SERVICECMD | Service command for System Controller to execute the request. |
For more information about system services, see PolarFire FPGA and PolarFire SoC FPGA System Services User Guide.