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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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5.0 Memory Organization  
CN8478/CN8474A/CN8472A/CN8471A  
5.2 Descriptors  
Multichannel Synchronous Communications Controller (MUSYCC™)  
In cases where both shared memory queue and internal queue are full and new  
descriptors are generated, those descriptors are discarded. MUSYCC indicates it  
has lost interrupts internally by overwriting the bit field ILOST in the last  
Interrupt Descriptor in the internal queue. The ILOST indication represents one  
or more lost descriptors.  
5.2.6.3 INTA* Signal  
Line  
The host must monitor the INTA* signal line at all times. An assertion on this line  
signifies the INTCNT filed in the Interrupt Status Descriptor is non-0. A non-0  
INTCNT signifies that Interrupt Descriptors have been written to the Interrupt  
Queue in shared memory.  
Upon detection of the INTA* assertion, the host must perform a direct read of  
the Interrupt Status Descriptor from within MUSYCC. This descriptor provides  
the offset to the location of the first unserviced descriptor in the queue, the  
number of unserviced descriptors, and determines if the queue is full.  
The INTCNT field is reset on each read of the Interrupt Status Descriptor.  
As the INTCNT is reset, the INTA* signal is deasserted.  
The host applies its interrupt service routines to service each of the  
descriptors. As the host finishes servicing a number of descriptors, it writes the  
offset to the location of the last serviced descriptor to the Interrupt Status  
Descriptor, NEXTINT. A write to this field indicates to MUSYCC that descriptor  
locations previously unserviced now have been serviced, and new descriptors can  
be written. MUSYCC continues to write to available space whether the host  
updates the NEXTINT field or not.  
NOTE: After reading the Interrupt Status Descriptor, the host services all  
unserviced descriptors (count of INTCNT starting at NEXTINT) in the  
queue at the time of the read. If the host is unsuccessful in servicing this  
set of descriptors, the host must provide an alternate method of tracking  
unserviced descriptors. Every read of the status descriptors provides  
information only on new descriptors placed in the queue autonomously by  
MUSYCC since the last time the status descriptor was read.  
5.2.6.4 INTB* Signal  
Line  
A second interrupt signal line, the PCI INTB* signal line, is asserted by  
MUSYCC when it detects an assertion on the EBUS EINT* signal line.  
MUSYCC does not generate descriptors or use the interrupt queue for this  
condition because it does not know the source or reason for the interrupt. The  
reason is external to MUSYCC. This signal acts as an interrupt line pass-through  
for devices connected to the EBUS. The EINT* signal line can be tied to interrupt  
one or more output pins of one or more peripheral devices. As MUSYCC detects  
EINT* assertion, MUSYCC asserts the INTB* towards the host as long as the  
EINT* remains asserted.  
5-46  
Conexant  
100660E  
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