cx28500 Mindspeed Technologies, cx28500 Datasheet - Page 126

• Manufacturer Part Number: cx28500
• Description: Cx28500 Multichannel Synchronous Communications Controller
• Manufacturer: Mindspeed Technologies

6.8.3.2
6.8.3.2.1
This register contains the Base Address of the Receive Head Pointer Table update during the CONFIG_WR SRQ.
6.8.3.2.2
For each message descriptor (MD) table, CX28500 maintains a pointer to its first MD copied from the head pointer
table and a pointer (actually the offset from the starting address of the current MD being processed). The length of
Receive Message Descriptor table is given by the fact that the MD is a 12-bit field in Receive Internal Message
Processing Table (RIMPT).
6.8.4
There are two CX28500 internal registers that contain the address of the Transmit and Receive Head Pointer Table
(i.e., THPT and RHPT).
These registers are updated with the values of THPT and RHPT during CONFIG_WR service request cycle. The
content of TBAHP or RBAHP register is described in
Table 6-37.
The content of each register (TBAHP or RBAHP) contains the starting address of the Transmit Head Pointer Table
(THPT) or Receive Head Pointer Table (RHPT), respectively.
The content of each THPT or RHPT table contains the address of the Message Descriptor Head Pointer Table, for
each independent channel (see
Table 6-38.
6.8.5
A message descriptor defines one data buffer where all or part of a message is stored in shared memory.
By allocating a number of message descriptors to the message descriptor table, numerous data buffers can be
linked together to support high-speed data links or large messages spread across a number of smaller data
buffers.
Depending on the transmission and reception rate of individual channels, the numbers and sizes of message
buffers can vary between channels and/or applications. For high-speed channels, more and larger buffers can be
28500-DSH-002-C
31:2
1:0
31:3
2:0
Bit
Bit
BAHPTBL[29:0]
BAHPTBL[1:0]
Field Name
Field Name
MDHP[28:0]
MDHP[2:0]
Transmit and Receive Base Address Head Pointer (TBAHP and RBAHP) Content
Transmit and Receive Head Pointer Table (THPT and RHPT) Content
Receive Path
Receive Base Address Head Pointer (RBAHP) (CONFIG_WR)
Receive Internal Message Processing Table (RIMPT)
Head Pointer Table and Its Content
Message Descriptor (MD)
Value
Value
000
—
00
—
Table
These 30 bits are appended with 00b to form a dword-aligned 32-bit address. This address points to
the first Head Pointer descriptor in the table of Head Pointers Descriptors in the Host Shared Memory.
Ensures dword alignment
These 29 bits are appended with 000b to form a 64-bit aligned address. This address points to the first
Message Descriptor in the table of message descriptors associated with a specific channel as
illustrated in
Ensures 64-bit alignment
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6-38).
Figure 6-3, Receive Message Data
Table
6-37.
®
Description
Description
Structures.
Memory Organization
111