參數(shù)資料
型號: AM79C970
廠商: Advanced Micro Devices, Inc.
英文描述: PCnetTM-PCI Single-Chip Ethernet Controller for PCI Local Bus
中文描述: PCnetTM - PCI單芯片以太網(wǎng)控制器的PCI總線
文件頁數(shù): 22/168頁
文件大?。?/td> 943K
代理商: AM79C970
P R E L I M I N A R Y
AMD
1-889
Am79C970
Bus Master DMA Transfers
There are four primary types of DMA transfers. The
PCnet-PCI controller uses non-burst as well as burst cy-
cles for read and write access to the main memory.
Basic Non-Burst Read Cycles
The PCnet-PCI controller uses non-burst read cycles to
access the initialization block and the receive and trans-
mit descriptor entries. Some of the read accesses to the
transmit buffer memory are also in non-burst mode. All
PCnet-PCI controller non-burst read accesses are of
the PCI command type Memory Read (type 6). Note that
during all non-burst read operations, the PCnet-PCI
controller will always activate all byte enables, even
though some byte lanes may not contain valid data as
indicated by a buffer pointer value. In such instances,
the PCnet-PCI controller will internally discard un-
needed bytes.
Figure 2 shows a typical non-burst read access. The
PCnet-PCI controller asserts
IRDY
at clock 5 immedi-
ately after the address phase and starts sampling
DEVSEL
. The target extends the cycle by asserting
DEVSEL
not until clock 6. Additionally, the target inserts
one wait state by asserting its ready (
TRDY
) at clock 8.
18220C-4
FRAME
CLK
AD
IRDY
TRDY
C/
BE
DEVSEL
REQ
GNT
1
2
3
4
5
6
7
8
0000
9
PAR
PAR
PAR
DATA
DEVSEL
is sampled by the PCnet-PCI controller.
ADDR
0110
Figure 2. Non-Burst Read Cycle With Wait States
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AM79C970A 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:PCnet-PCI II Single-Chip Full-Duplex Ethernet Controller for PCI Local Bus Product
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AM79C970AKC\W 制造商:Rochester Electronics LLC 功能描述:- Bulk