CX82100 Home Network Processor Data Sheet
4.6
Three Basic Modes of Address Generation
4.6.1
Source or Destination Mode
DMAC_{x}_Ptr1 is initialized by the microcontroller to point to the beginning of a
dword-aligned source or destination buffer. This pointer advances (by 1 qword) after
each transfer request X{x}R. Reading this pointer returns the current qword location to
be handled next by the DMAC when it processes the channel request.
4.6.2
Circular Buffer Modes
Two circular buffer modes are supported:
•
•
The direct circular buffer for the downstream USB receive data channels.
The indirect circular pointer table for the Ethernet receive channels.
Direct Circular Buffer
Figure 4-1 depicts how the addresses are generated in the Direct Circular Buffer mode.
Figure 4-1. Address Generation in Direct Circular Buffer Mode
8 Bytes
Top
Base Pointer
DMAC_{x}_Ptr2
(Fixed)
∆ = DMAC_{x}_Cnt2
-
∆
+
8*∆
DMAC_{x}_Cnt1
Current Pointer DMAC_{x}_Ptr1
(Fixed)
DMAC_{x}_Cnt1
-1
Bottom
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4-6
Conexant Proprietary and Confidential Information
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CONEXANT [ CONEXANT SYSTEMS, INC ]
