SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
To perform internal transfers through the configuration bus, set the XBUSEL/RBUSEL bit to 1 in the MCASP_XFMT/MCASP_RFMT registers, respectively. Failure to do so may result in software malfunction.
MCASP[0-2] whose data ports are accessible directly via CBASS0 do not support FIFO/constant addressing modes. Incrementing transfers must be used instead.
In this method, the CPU accesses the XRBUFn transmit or receive buffer through corresponding configuration bus (CFG) address.
The exact XRBUFn transmit/receive buffer physical address for any particular serializer is determined by adding the transmit/receive buffer alias register offset for that particular serializer to the base address of MCASP CFG port actual for CBASS0 accesses. The XRBUFn buffer of the n-th serializer configured as a transmitter is aliased - MCASP_XBUFn in the CFG port address space. For example, the XRBUF2 transmit buffer is mapped as the MCASP_XBUF2 register. Similarly, the XRBUFn buffer of the n-th serializer configured as a receiver is aliased - MCASP_RBUFn in the CFG port address space. For example, the XRBUF3 receive buffer is mapped as the MCASP_RBUF3 register.
Accessing the XRBUF through the DATA port (see Section 12.5.2.3.11.1.3) is different than CFG port accesses because the DATA port access demands the same physical address, regardless of transfer direction or current channel index , while accessing through the peripheral configuration port - CFG, the CPU must provide the exact MCASP_XBUFn or MCASP_RBUFn address upon accessing n-th serializer TX or RX buffer, respectively. For more details about MCASP_XBUFn and MCASP_RBUFn addresses corresponding to MCASP CFG port, see CFG Registers (n = 0 to 15).