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CN8474AEPF 参数 Datasheet PDF下载

CN8474AEPF图片预览
型号: CN8474AEPF
PDF下载: 下载PDF文件 查看货源
内容描述: 多通道同步通信控制器( MUSYCC ™ ) [Multichannel Synchronous Communications Controller (MUSYCC?)]
分类和应用: 通信控制器
文件页数/大小: 221 页 / 2104 K
品牌: CONEXANT [ CONEXANT SYSTEMS, INC ]
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CN8478/CN8474A/CN8472A/CN8471A  
6.0 Basic Operation  
Multichannel Synchronous Communications Controller (MUSYCC™)  
6.3 Channel Operation  
6.3.12 Receive Time Slot Map  
Same as Transmit Time Slot Map.  
6.3.13 Receive Subchannel Map  
Same as Transmit Subchannel Map.  
6.3.14 Receive Channel Configuration Descriptor  
Same as Transmit Channel Configuration Descriptor.  
6.3.15 Message Lists  
Message lists contain data transmitted or received by MUSYCC. Message lists  
always reside in shared memory. Upon channel activation, MUSYCC traverses  
the list and either takes data from data buffers (Tx) or puts data into data buffers  
(Rx). Each direction of a channel must be assigned a message list before the  
direction of that channel is activated.  
A message list is a singly-linked list of Message Descriptors. A Message  
Descriptor consists of a Buffer Descriptor (1 dword), a Data Pointer (1 dword),  
and a Next Descriptor Pointer (1 dword). (For further information, refer to  
Table 5-19, Message Descriptor).  
The Buffer Descriptor contains a set of bit fields which instruct MUSYCC  
how to behave after the data is put in or taken out of a data buffer.  
The Data Pointer contains an address in shared memory where MUSYCC can  
take data to be transmitted or store data received from the corresponding channel.  
The Next Descriptor Pointer contains an address of a Message Descriptor in  
shared memory where MUSYCC can access the “next” Message Descriptor in the  
linked list.  
To terminate a message list, the contents of the Next Descriptor Pointer in the  
last descriptor in a list can point either to the address of the last descriptor or to a  
general purpose “terminate” Message Descriptor that can be used by any message  
list to represent the end of the list. Thus, the OWNER bit field in the last  
descriptors Buffer Descriptor must eventually indicate that the host owns the  
buffer. This bit value is opposite for receive and transmit buffer ownership.  
The OWNER bit field mechanism controls the termination of the message list  
as MUSYCC reads in each Message Descriptor in the linked list: it first checks  
the OWNER bit field to see if it, and not the host, owns the buffer. If it does own  
the descriptor, after servicing the contents of this descriptor, MUSYCC reverses  
the OWNER bit field to hand the descriptor back to the host; if it does not own the  
buffer, the end of the message list is automatically concluded. The channel stays  
active and, depending on other bit field values in the Buffer Descriptor,  
MUSYCC either polls this last descriptor regularly to see if the OWNER bit value  
has changed, or it idles the channel and awaits another channel activation or  
channel jump request. The former is useful in continuing a message list while  
retaining the original list. The latter is useful in starting a message list from the  
top element in the list.  
The host processor must never change a descriptor in a buffer to which it has  
already granted MUSYCC ownership. The Owner bit is the only handshake  
mechanism to prevent race conditions.  
100660E  
Conexant  
6-19  
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