SPRUJ53B April 2024 – September 2024 TMS320F28P550SJ , TMS320F28P559SJ-Q1
The FSI transmitter can supply the CRC to the frame being transmitted through the embedded hardware CRC submodule or by supplying a user-defined value. This is controlled by setting TX_OPER_CTRL_LO.SW_CRC appropriately.
If hardware CRC generation is selected (TX_OPER_CTRL_LO.SW_CRC = 0, the default), the CRC is computed by hardware on the data and user data fields using the CRC polynomial 0x7 (x8 + x2 + x + 1). The transmitter module automatically computes the CRC on the data fields without user intervention when the frame is transmitted. For more information on how the CRC is generated by the CRC submodule, refer to Section 25.3.7.
If software CRC generation is selected (TX_OPER_CTRL_LO.SW_CRC = 1), the CRC must be computed by software and placed in the TX_USER_CRC register. The next frame to be transmitted uses the value placed in the TX_USER_CRC register in place of the CRC value generated by the hardware.
As the TX_USER_CRC register is software-programmable, the application can use this field as an extra data field for application-specific purposes. If TX_USER_CRC is used in this manner, the CRC detection on the receiver is not valid and must be ignored.