
RELEASED
DATA SHEET
PM7366 FREEDM-8
ISSUE 4
PMC-1970930
FRAME ENGINE AND DATA LINK MANAGER
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA,INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
48
Field
Description
V
This bit (Valid) indicates whether a packet is currently being
received on the DMA channel. When the V bit is set to 1, the other
fields in the RCDR table entry for the DMA channel contain valid
information.
Start RPD Pointer[13:0]
This field contains the pointer to the first RPD for the packet being
received.
DMA Current
Address[31:0]
The DMA Current Address [31:0] bits holds the host address of the
next dword in the current buffer. The RMAC increments this field on
each access to the buffer.
9.4.2
DMA Transaction Controller
The DMA Transaction Controller coordinates the reception of data packets from the Receive
Packet Interface and their subsequent storage in host memory. A packet may be received over a
number of separate transactions, interleaved with transactions belonging to other DMA channels.
As well as sending the received data to host memory, the DMA Transaction Controller initiates
data transactions of its own for the purposes of maintaining the data structures (queues,
descriptors, etc.) in host memory.
9.4.3
Write Data Pipeline/Mux
The Write Data Pipeline/Mux performs two functions. First, it pipelines receive data between the
RHDL block and the GPIC block, inserting enough delay to enable the DMA Transaction Controller
to generate appropriate control signals at the GPIC interface. Second, it provides a multiplexor to
the data out lines on the GPIC interface, allowing the DMA Transaction Controller to output data
relating to the transactions the controller itself initiates.
9.4.4
Descriptor Information Cache
The Descriptor Information Cache provides the storage for the Receive Channel Descriptor
Reference (RCDR) Table described above (Figure 8).
9.4.5
Free Queue Cache
The Free Queue Cache block implements the 6 element RPDR Small Buffer Free Queue cache
and the 6 element RPDR Large Buffer Free Queue cache. These caches are used to store free
small buffer and large buffer RPDRs. Caching RPDRs reduces the number of host bus accesses
that the RMAC makes.
Each cache is managed independently. The elements of the cache are consumed one at a time
as they are needed by the RMAC. The RPDR small buffer cache is reloaded when it is empty and
the RMAC requires a new small buffer RPDR. The large buffer RPDR cache is reloaded when it