参数资料
型号: IBM21P100BGC
元件分类: 总线控制器
英文描述: PCI BUS CONTROLLER, PBGA304
封装: 31 X 31 MM, PLASTIC, BGA-304
文件页数: 109/144页
文件大小: 5197K
代理商: IBM21P100BGC
IBM21P100BGC
IBM 133 PCI-X Bridge R2.0
ppb20_pcix_regs.fm.01
October 15, 2001
Configuration Registers
Page 67 of 144
5.2.5.2 Secondary Data Buffering Control Register
This register provides controls for memory read transactions that are initiated on the secondary interface.
Address Offset
x‘42’
Access
See individual bit fields.
Reset Value
x‘0020’
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15 14 13 12 11 10
9
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6
5
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2
1
0
Bit(s)
Access
Field Name and Description
15
RO
Reserved
14:12
RW
Maximum Memory Read Byte Count
These bits set the maximum byte count used by the bridge when generating read requests on the primary
bus in response to a memory read operation initiated on the secondary bus (when the secondary bus is in
the PCI mode). Device drivers must not modify these bits without considering the impact on the rest of the
system. These bits only have an effect if the prefetch mode bits for the PCI read command in use (bits (9:8),
(7:6), or (5:4) below) are set to “full prefetch”. The most recent value of this register is used each time the
bridge makes a new read request. The bits have the following meaning:
000
Default to 512 bytes.
001
128 bytes.
010
256 bytes.
011
512 bytes.
100
1024 bytes.
101
2048 bytes.
110
4096 bytes.
111
Default to 512 bytes.
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