PM7384 FREEDM-84P672
DATA SHEET
PMC-1990445
ISSUE 5
FRAME ENGINE AND DATA LINK MANAGER 84P672
decrease the number of host bus accesses required to process each data
packet. The structure of the RCDR table is shown in Figure 8.
Figure 8 – Receive Channel Descriptor Reference Table
Bit 31
Bit 0
RPD Pointer[14:0]
Start RPD Pointer[14:0]
RBC[1:0]
RCC 0 Bytes Avail. in Buffer[14:0]
Buffer Size[14:0]
Res
V
DMA Current Address[31:0]
RBC[1:0]
Bytes Avail. in Buffer[14:0]
Buffer Size[14:0]
RCC 1
RPD Pointer[14:0]
Start RPD Pointer[14:0]
Res
V
DMA Current Address[31:0]
RBC[1:0]
RCC 671 Bytes Avail. in Buffer[14:0]
Buffer Size[14:0]
RPD Pointer[14:0]
Start RPD Pointer[14:0]
Res
V
DMA Current Address[31:0]
Table 10 – 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.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
51
PMC [ PMC-SIERRA, INC ]
