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參數(shù)資料
| 型號： | AM79C974 |
| 廠商： | Advanced Micro Devices, Inc. |
| 英文描述： | PCnetTM-SCSI Combination Ethernet and SCSI Controller for PCI Systems |
| 中文描述： | PCnetTM -的SCSI結(jié)合以太網(wǎng)和SCSI控制器PCI系統(tǒng) |
| 文件頁數(shù)： | 150/153頁 |
| 文件大?。?/td> | 838K |
| 代理商： | AM79C974 |
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AMD
A M E N D M E N T
16
Am79C974
DMA Scatter-Gather Mechanism
The Am79C974 contains a scatter-gather translation
mechanism which facilitates faster data transfers. This
feature uses a
M
emory
D
escriptor
L
ist (a list of contigu-
ous physical memory addresses) which is stored in sys-
tem memory. Use of the Memory Descriptor List allows
a single SCSI transfer to be read from (or written to) non-
contiguous physical memory locations. This mecha-
nism avoids copying the transfer data and MDL list,
which was previously required for conventional DMA
operations.
Memory Descriptor List (MDL)
The MDL is a non-terminated (no End Of File marker)
list of 32-bit page frame addresses, which is always
aligned on a Double Word boundary. The format is
shown below:
31
12 11
0
Page Frame Address
Ignored
DMA Scatter-Gather Operation
(4k aligned elements)
The scatter-gather mechanism described below
assumes 4k page alignment and size for all MDL entries
except the first and last entry. This feature is enabled by
setting the MDL bit in the DMA Command register (Bit 4,
Address (B)+40h).
1. a) Prepare the Memory Descriptor List (MDL)
through software and store it in system
memory.
b) Load the address of the starting entry in the
Memory Descriptor List (MDL) into the Start
Memory Descriptor List Address (SMDLA)
register. This value is automatically copied into
the Working MDL Address Counter (WMAC).
c) Program the Starting Transfer Count (STC)
register with the total transfer length (i.e., # of
bytes). Also program the Starting Physical
Address (SPA) register (bits 11:0) with the
starting offset of the first entry.
Note
: The value in the SMDLA register must be double
word aligned. Therefore, read/write transactions will al-
ways begin on a double word boundary.
18681A/1-31
0
31
0
31
SMDLA
WMAC
0
12
31
Page Frame Address #1
Page Frame Address #2
Page Frame Address #3
Page Frame Address #4
MDL
Ignored
Page Frame Address #n
Ignored
Ignored
Ignored
Ignored
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AM79C974KCW | PCnetTM-SCSI Combination Ethernet and SCSI Controller for PCI Systems |
| AM79C975 | PCnet⑩-FAST III Single-Chip 10/100 Mbps PCI Ethernet Controller with Integrated PHY |
| AM79C973 | PCnet⑩-FAST III Single-Chip 10/100 Mbps PCI Ethernet Controller with Integrated PHY |
| AM79C973KCW | PCnet⑩-FAST III Single-Chip 10/100 Mbps PCI Ethernet Controller with Integrated PHY |
| AM79C975KCW | PCnet⑩-FAST III Single-Chip 10/100 Mbps PCI Ethernet Controller with Integrated PHY |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AM79C974KC | 制造商:Advanced Micro Devices 功能描述: |
| AM79C974KC/W | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LAN Node Controller |
| AM79C974KCW | 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:PCnetTM-SCSI Combination Ethernet and SCSI Controller for PCI Systems |
| AM79C975 | 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:PCnet⑩-FAST III Single-Chip 10/100 Mbps PCI Ethernet Controller with Integrated PHY |
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