SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
The associated static Transfer Request (TR) operations of PDMA0, located in front of MCASP, must be configured to match the MCASP configuration. For more information, refer to DMA Controllers.
The typical scenario is to use the DMA to service the MCASP transmit and receive logic through the DATA port. The transfer passes through integrated AFIFO transmit/receive buffer. If AFIFO is enabled, DMA requests are collected and fed to a device DMA controller (see Figure 12-265). The data transfer is managed by the AFIFO according to generated transmit and receive events in the MCASP and data is fed to transmit buffers and fetched from receive buffers as described in Section 12.5.2.3.12, MCASP Audio FIFO (AFIFO). The generation of transmit and receive request is described below. After generation of transmit/receive DMA events from MCASP module, these events are collected in AFIFO and on specific AFIFO conditions described in Section 12.5.2.3.12, MCASP Audio FIFO (AFIFO) the requests (transmit or receive) are forwarded to a DMA controller via MCASP[0-2]_XMIT_DMA_EVT and MCASP[0-2]_REC_DMA_EVT outputs. If the AFIFO is disabled (default state) it is transperrant for the MCASP module and all request are directly sent to the DMA controller.
In transmit mode, the DMA event - XINT (MCASP[0-2]_XMIT_DMA_EVT output), which is triggered upon each XDATA transition from 0 to 1, is used to service the MCASP TXBUFn transmit buffers. In receive mode, the DMA event RINT (MCASP[0-2]_REC_DMA_EVT output) which is triggered upon each RDATA transition from 0 to 1, is used to service the MCASP RXBUFn receive buffers.
Figure 12-276 is an example of an audio system with six audio channels (LF, RF, LS, RS, C and LFE) transmitted or received through the MCASP signals - AXR0, AXR1 and AXR2. It shows the points at which events XINT/RINT are triggered.
In Figure 12-276, a Tx DMA event XINT is triggered on each time slot. In the example, XINT is triggered for each of the transmit audio channel time slot (time slot for channels LF, LS, and C; and time slot for channels RF, RS, LFE). Transmit DMA events are generated automatically upon transmit data ready, provided that DMA TX requests generation is enabled in the MCASP_XEVTCTL register. Similarly, Rx DMA event RINT is triggered for each of the receive audio channel time slot. Receive DMA events are generated automatically upon receive data ready, provided that DMA RX requests generation is enabled in the MCASP_PIDTCTL register.