
RELEASED
DATA SHEET
PM7380 FREEDM-32P672
ISSUE 5
PMC-1990262
FRAME ENGINE AND DATA LINK MANAGER 32P672
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA,INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
55
decrease the number of host bus accesses required to process each data
packet. The structure of the RCDR table is shown in Figure 9.
Figure 9 – Receive Channel Descriptor Reference Table
RPD Pointer[14:0]
Bytes Avail. in Buffer[14:0]
Start RPD Pointer[14:0]
DMA Current Address[31:0]
RBC[1:0]
Bit 0
Bit 31
RCC 0
RCC 1
RCC 671
RPD Pointer[14:0]
Start RPD Pointer[14:0]
DMA Current Address[31:0]
RPD Pointer[14:0]
Start RPD Pointer[14:0]
DMA Current Address[31:0]
Buffer Size[14:0]
Buffer Size[14:0]
Buffer Size[14:0]
V
V
V
Bytes Avail. in Buffer[14:0]
RBC[1:0]
Bytes Avail. in Buffer[14:0]
RBC[1:0]
Res
Res
Res
Table 8 – Receive Channel Descriptor Reference Table Fields
Field
Description
Bytes Available in
Buffer[15:0]
This field is used to keep track of the number of bytes
available in the current data buffer. The RMAC672
initialises the Bytes Available in Buffer to the Receive
Buffer Size minus the offset at the head of the buffer.
The field is decremented each time a byte is written into
the buffer.
RBC[1:0]
This field is used to keep track of the number of buffers
used when storing ‘raw’ (i.e. non packet delimited) data.
The RMAC672 initialises the RBC field to the value of
the RAWMAX[1:0] field in the RMAC Control Register.
The field is decremented each time a buffer is filled with
data. If the field reaches zero, the chain of RPDs is
placed on the ready queue and a new chain started.
RPD Pointer[14:0]
This field contains the pointer to the current RPD.