www.ti.com

Figure 21. CPPI Boundary Diagram

 

Peripheral￿boundary

 

CPPI￿block

 

 

 

 

Config￿bus￿access

32

CPPI control

32

 

32

registers

Buffer

 

 

descriptor

 

 

 

dual-port

 

 

 

SRAM

 

 

 

(Nx20B)

 

Data buffer

DMA

128

 

 

 

 

SRIO Functional Description

CPU

L2￿memory

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 32-bit data words aligned on a 32-bit boundary.

Table 19. TX DMA State Head Descriptor Pointer (HDP) (Address Offset 500h–53Ch)

Bit

Name

Description

31–0

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

 

 

operations and is zeroed by the port when all packets in the queue have been transmitted. An error

 

 

condition results if the DSP core writes this field when the current field value is nonzero. The

 

 

address must be 32-bit word aligned.

SPRUE13A –September 2006

Serial RapidIO (SRIO)

51

Submit Documentation Feedback

Page 51
Image 51
Texas Instruments TMS320TCI648x manual Cppi Boundary Diagram, TX Operation