SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
Traffic for which the pixel rate is imposed by the camera is qualified as hard real time traffic. Example of such hard real time traffic is data received from the camera (through PPI), optionally processed in the CAL and then sent to SDRAM using the OCPO port.
Hard real time traffic cannot be stalled for long periods of time. Indeed, the camera sends data at constant speed and it can only be stalled until FIFOs on the path are filled up. When FIFOs become full, data is discarded and the frame is therefore corrupted. To minimize the risk of real time data corruption, the device supports a mechanism that is activated by the MFlag generated by real time initiators.
MFlag generation must be disabled (through CAL_CTRL[20:13] MFLAGL = 0xFF and CAL_CTRL[31:24] MFLAGH = 0xFF), when CAL does not generate any real time traffic.
Static assertion of MFlag is only supported for debug purposes and must not be enabled for normal utilization (CAL_CTRL[20:13] MFLAGL = 0x00 -> MFlag=0x11; CAL_CTRL[20:13] MFLAGL = 0xFF and CAL_CTRL[30:24] MFLAGH = 0x00 -> MFlag=0x01).
Dynamic MFlag generation is to be used when the Write DMA operates on real time data. In that case, the MFlag value depends on the number of slots (n) ready to generate transactions in the Write DMA:
Software must ensure that: