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Figure 21. CPPI Boundary Diagram
| Peripheralboundary |
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CPPIblock |
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| Configbusaccess | 32 | |
CPPI control | 32 |
| 32 |
registers | Buffer | ||
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| descriptor |
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| SRAM |
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| (Nx20B) |
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Data buffer | DMA | 128 |
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SRIO Functional Description
CPU
L2memory
2.3.4.2TX Operation
Outgoing messages are handled similarly, with buffer descriptor queues that are assigned by the CPUs. The queues are configured and initialized upon reset. When a CPU wants to send a message to an external RapidIO device, it writes the buffer descriptor information via the configuration bus into the SRAM. Again, there is a single buffer descriptor per RapidIO message. Upon completion of writing the buffer descriptor, the OWNERSHIP bit is set to give control to the peripheral. The CPU then writes the TX DMA State HDP register to initiate the queue transmit. For TX operation, PortID is specified to direct the outgoing packet to the appropriate port. Table 19 and Table 20 describe the TX DMA state registers. Figure 22 shows the TX buffer descriptor fields and Table 21 describes them. A TX buffer descriptor is a contiguous block of four
Table 19. TX DMA State Head Descriptor Pointer (HDP) (Address Offset
Bit | Name | Description |
TX Queue Head | TX Queue Head Descriptor Pointer: This field is the DSP core memory address for the first buffer | |
| Descriptor Pointer | descriptor in the transmit queue. This field is written by the DSP core to initiate queue transmit |
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| operations and is zeroed by the port when all packets in the queue have been transmitted. An error |
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| condition results if the DSP core writes this field when the current field value is nonzero. The |
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| address must be |
SPRUE13A | Serial RapidIO (SRIO) | 51 |