SPRUIV7B May 2022 – September 2023 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP
The CRC16/32 module directly connects with the PRU internal registers R25-R29 through use of the PRU broadside interface and XFR instructions. Table 7-59 shows the functionality of each register.
The XFR instructions (XIN/XOUT/XCHG) are used to load/store register contents between the PRU core and the CRC16/32 module. These instructions define the start, size, direction of the operation, and device ID. The XFR device ID number corresponding to the CRC16/32 module is 1.
CRC Register | R/W | Description | PRU Mapping |
---|---|---|---|
CRC_CFG | W | Always write all 4 bytes. bit [0] CRC32_ENABLE: 0: CRC16 mode is selected. Hardware will auto-set init state of CRC_SEED to 0000_0000h. However, for CRC16-CCITT software will need to write the init state of FFFF_FFFFh to CRC_SEED. Note: The CRC16 result value is only 16-bits. 1: CRC32 mode is selected. Hardware will auto-set init state of CRC_SEED will be FFFF_FFFFh. bit [1] CRC_32B_NOT_EMPTY: 0: CRC 32Byte buffer is empty 1: CRC 32Byte buffer is not empty bit [2] CRC16_MOD_ENABLE: 0: CRC16 (x16+x15+x2+1 ) 1: CRC16-CCITT (x16+x12+x5+1 ) - Note: CRC32_ENABLE field must = 0. | R25 |
CRC_DATA_8_BFLIP | R | 8-bit flip of CRC_DATA. CRC_DATA_8_BFLIP has the same byte order as CRC_DATA[31-0], but each byte has all bits flipped. CRC_DATA_32_FLIP[7-0] = CRC_DATA[0-7] CRC_DATA_32_FLIP[15-8] = CRC_DATA[8-15] CRC_DATA_32_FLIP[23-16] = CRC_DATA[16-23] CRC_DATA_32_FLIP[31-24] = CRC_DATA[24-31] For CRC16, only CRC_DATA_8_BFLIP[15-0] are valid. No auto reset on CRC_DATA_8_BFLIP read. | R27 |
CRC_SEED | W | CRC SEED value. Hardware will auto-initialize the CRC_SEED value to 0000_0000h for CRC16 and FFFF_FFFFh for CRC32. Software only needs to initialize CRC_SEED if a different default value is required. For CRC16-CCITT, software needs to update initial CRC_SEED value to FFFF_FFFFh. Always write 4 bytes. Note: Reading the CRC_DATA register will reset the CRC value to the CRC_SEED state. | R28 |
CRC_DATA_32_BFLIP | R | Full 32-bit flip of CRC_DATA CRC_DATA_32_BFLIP[0] = CRC_DATA[31] … CRC_DATA_32_BFLIP[31] = CRC_DATA[0] For CRC16, only CRC_DATA_32_BFLIP[31-16] are valid. No auto reset on CRC_DATA_32_BFLIP read. | R28 |
CRC_DATA | RW | For Write, must use a fixed width throughout the session. The CRC module supports lower 8-bit, or lower 16-bit, or full 32-bit data widths. For Read, LSB or CRC_DATA[0] is first bit on the wire. For Read, reset the CRC_DATA back to CRC_SEED state. Note: Firmware must add 1 to 2 NOPs after the last XOUT to the XIN. For CRC16, only CRC_DATA[15-0] is valid. | R29 |