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): 67/168頁
文件大?。?/td> 943K
代理商: AM79C970
AMD
P R E L I M I N A R Y
1-934
Am79C970
Table 6 describes all possible bus master accesses that
the PCnet-PCI controller will perform. The right most
column lists all operations that may execute the given
access:
Table 6. Bus Master Accesses
Access
Mode
BE
[3:0]
Operation
4-byte read
Read
0000
descriptor read
or initialization block read
or transmit data buffer read
4-byte write
Write
0000
descriptor write
or receive data buffer write
3-byte write
Write
1000
receive data buffer write
3-byte write
Write
0001
receive data buffer write
2-byte write
Write
1100
receive data buffer write
2-byte write
Write
1001*
receive data buffer write
2-byte write
Write
0011
receive data buffer write
1-byte write
Write
1110
receive data buffer write
1-byte write
Write
1101*
receive data buffer write
1-byte write
Write
1011*
receive data buffer write
1-byte write
Write
0111
descriptor write
or receive data buffer write
* Cases marked with an asterisk represent extreme boundary conditions that are the result of programming one- and two-byte
buffer sizes, and therefore will not be seen under normal circumstances.
Note that all PCnet-PCI controller master read opera-
tions will always activate all byte enables. Therefore, no
one-, two- or three-byte read operations are indicated in
the table.
In the instance where a transmit buffer pointer address
begins on a non-DWORD boundary, the pointer will be
truncated to the next DWORD boundary address that
lies below the given pointer address and the first read
access from the transmit buffer will be indicated on the
byte enable signals as a four-byte read from this ad-
dress. Any data from byte lanes that lie outside of the
boundary indicated by the buffer pointer will be dis-
carded inside of the PCnet-PCI controller. Similarly, if
the end of a transmit buffer occurs on a non-DWORD
boundary, then all byte lanes will be indicated as active
by the byte enable signals, and any data from byte lanes
that lie outside of the boundary indicated by the buffer
pointer will be discarded inside of the PCnet-PCI
controller.
Slave Access to I/O Resources
The PCnet-PCI device is always a 32-bit peripheral on
the system bus. However, the width of individual soft-
ware resources on board the PCnet-PCI controller may
be either 16-bits or 32-bits. The PCnet-PCI controller
I/O resource widths are determined by the setting of the
DWIO bit as indicated in the following table:
PCnet-PCI
Controller I/O
DWIO Setting Resource Width Example Application
DWIO = 0
16-bit
Existing PCnet-ISA
driver that assumes
16-bit I/O mapping
and 16-bit resource
widths
DWIO = 1
32-bit
New drivers written
specifically for the
PCnet-PCI controller
Note that when I/O resource width is defined as 32 bits
(DWIO mode), the upper 16 bits of the I/O resource is
reserved and written as ZEROS and read as undefined,
except for the APROM locations and CSR88.The
APROM locations and CSR88 are the only I/O re-
sources for which all 32 bits will have defined values.
However, this is true only when the PCnet-PCI controller
is in DWIO mode.
Configuring the PCnet-PCI controller for DWIO mode is
accomplished whenever there is any attempt to perform
a 32-bit write access to the RDP location (offset 10h).
See the DWIO section for more details.
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