CN8478 Datasheet, PDF (123/221 Pages) Conexant Systems, Inc – Multichannel Synchronous Communications Controller (MUSYCC)

CN8478/CN8474A/CN8472A/CN8471A
Multichannel Synchronous Communications Controller (MUSYCC™)
5.0 Memory Organization
5.2 Descriptors
5.2.4.8 Next Message
Pointer
The Next Message Pointer is a 32-bit dword-aligned address pointing to the first
dword of a Message Descriptor which is next in a list of descriptors.
Table 5-26 lists the Next Descriptor Pointer and its description. The last Next
Message Pointer should point to the first Message Descriptor and not to itself.
Table 5-26. Next Descriptor Pointer
Bit
Field
Name
Value
31:2
NEXTPTR[29:0]
1:0
NEXTPTR[1:0]
0
Description
These 30 bits are appended with 00b to form a dword-aligned 32-bit address.
This address points to the next message descriptor in the list.
Ensures dword alignment.
5.2.4.9 Data Buffer
Pointer
The Data Buffer Pointer is a 32-bit address to the first byte of a data message in
shared memory. This pointer does not have to be word- or dword-aligned.
Table 5-27 lists the Data Buffer Pointer and its description.
Table 5-27. Data Buffer Pointer
Bit
Field
Name
Value
31:0
DATAPTR[31:0]
Description
The 32-bit address in this descriptor serves as a byte pointer to the first octet of a
data buffer.
5.2.4.10 Message
Descriptor Handling
The bit fields Inhibit Buffer Status Descriptor (INHTBSD for transmitters or
INHRBSD for receivers) in the Group Configuration Descriptor specify whether
or not MUSYCC writes a Buffer Status Descriptor to shared memory after the
end of the current message has been detected.
If INHTBSD/INHRBSD is set to 0, MUSYCC:
1. Assumes the Message Pointer points to the current Message Descriptor.
2. Overwrites the Buffer Descriptor field with the Buffer Status Descriptor
field.
3. Fetches the next Message Pointer from the descriptor.
4. Reads the next Message Descriptor.
5. Writes the pointer to the new descriptor into the Message Pointer in shared
memory.
If INHTBSD/INHRBSD is set to 1, MUSYCC:
1. Assumes the Message Pointer points to the next Message Descriptor.
2. Reads the next Message Descriptor.
3. Writes the Next Message Pointer from the descriptor into the Message
Pointer in shared memory.
100660E
Conexant
5-37