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參數(shù)資料
| 型號： | DS3134 |
| 廠商： | DALLAS SEMICONDUCTOR |
| 元件分類： | Digital Transmission Controller |
| 英文描述： | DATACOM, FRAMER, PBGA256 |
| 封裝： | 27 X 27 MM, PLASTIC, BGA-256 |
| 文件頁數(shù)： | 8/203頁 |
| 文件大?。?/td> | 777K |
| 代理商： | DS3134 |
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DS3134
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8.1.3 FREE QUEUE
The Host will write to the Receive Free Queue, the 32-bit addresses of the available (i.e. free) data buffers
and their associated Packet Descriptors. The descriptor space is indicated via a 16-bit pointer which the
DMA will use along with the Receive Packet Descriptor Base Address to find the exact 32-bit address of
the associated Receive Packet Descriptor.
Receive Free Queue Descriptor Figure 8.1.3A
dword 0
Free Data Buffer Address (32)
dword 1
Unused (16)
Free Packet Descriptor Pointer (16)
Note: The organization of the Free Queue is not affected by the enabling of Big Endian
dword 0; Bits 0 to 31 / Data Buffer Address. Direct 32-bit starting address of a free data buffer.
dword 1; Bits 0 to 15 / Free Packet Descriptor Pointer. This 16-bit value is the offset from the
Receive Descriptor Base Address of the free descriptor space associated with the free data buffer in dword
0. Note: This is an index not an absolute address.
dword 1; Bits 16 to 31 / Unused. Not used by the DMA. Can be set to any value by the Host and will
be ignored by the Receive DMA.
The Receive DMA will read from the Receive Free Queue Descriptor circular queue which data buffers
and their associated descriptors are available for use by the DMA.
The Receive Free Queue Descriptor is actually a set of two circular queues. See Figure 8.1.3B. There is
one circular queue that indicates where free large buffers and their associated free descriptors exist and
there is another circular queue that indicates where free small buffers and their associated free descriptors
exist.
Large and Small Buffer Size Handling
Via the Receive Configuration RAM Buffer Size field, the DMA knows for a particular HDLC channel,
whether the incoming packets should be stored in the large or the small free data buffers. The Host
informs the DMA of the size of both the large and small buffers via the Receive Large and Small Buffer
Size (RLBS/RSBS) registers. For example, when the DMA knows that data is ready to be written onto
the PCI Bus, it checks to see if the data is to be sent to a large buffer or a small buffer and then it goes to
the appropriate Free Queue Descriptor and pulls the next available free buffer address and free descriptor
pointer. If the Host wishes to have only one buffer size, then the Receive Free Queue Small Buffer Start
Address will be set equal to the Receive Free Queue End Address and in the Receive Configuration
RAM, none of the active HDLC channels will be configured for the small buffer size.
To keep track of the addresses of the dual circular queues in the Receive Free Queue, there are a set of
internal addresses within the device that are accessed by both the Host and the DMA. On initialization,
the Host will configure all of the registers shown in Table 8.1.3B. After initialization, the DMA will only
write to (i.e. change) the read pointers and the Host will only write to the write pointers.
相關PDF資料 |
PDF描述 |
|---|---|
| DS3150QN | DATACOM, PCM TRANSCEIVER, PQCC28 |
| DS3150Q | DATACOM, PCM TRANSCEIVER, PQCC28 |
| DS3150TN | DATACOM, PCM TRANSCEIVER, PDIP48 |
| DS3150T | DATACOM, PCM TRANSCEIVER, PQFP48 |
| DS5000FP-12 | 8-BIT, 12 MHz, MICROCONTROLLER, PQFP80 |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| DS-313PIN | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Analog Miscellaneous |
| DS-313-PIN | 功能描述:信號調(diào)節(jié) RoHS:否 制造商:EPCOS 產(chǎn)品:Duplexers 頻率:782 MHz, 751 MHz 頻率范圍: 電壓額定值: 帶寬: 阻抗:50 Ohms 端接類型:SMD/SMT 封裝 / 箱體:2.5 mm x 2 mm 工作溫度范圍:- 30 C to + 85 C 封裝:Reel |
| DS31400 | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:8-Input, 14-Output, Dual DPLL Timing IC with Sub-ps Output Jitter |
| DS31400DK | 功能描述:時鐘和定時器開發(fā)工具 DS31400 Dev Kit RoHS:否 制造商:Texas Instruments 產(chǎn)品:Evaluation Modules 類型:Clock Conditioners 工具用于評估:LMK04100B 頻率:122.8 MHz 工作電源電壓:3.3 V |
| DS31400GN | 功能描述:計時器和支持產(chǎn)品 Not Available From Mouser RoHS:否 制造商:Micrel 類型:Standard 封裝 / 箱體:SOT-23 內(nèi)部定時器數(shù)量:1 電源電壓-最大:18 V 電源電壓-最小:2.7 V 最大功率耗散: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝:Reel |
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