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AM79C978KC/W 参数 Datasheet PDF下载

AM79C978KC/W图片预览
型号: AM79C978KC/W
PDF下载: 下载PDF文件 查看货源
内容描述: 单芯片1/10 Mbps的PCI家庭网络控制器 [Single-Chip 1/10 Mbps PCI Home Networking Controller]
分类和应用: 控制器PC
文件页数/大小: 261 页 / 3499 K
品牌: AMD [ AMD ]
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Bit  
Name  
Description  
match due to delays in the part  
used to make up the final IPG.  
Changes should be added or sub-  
tracted from the provided hex val-  
ue on a one-for-one basis.  
31-4 RES  
Reserved locations. Written as  
zeros and read as undefined.  
3
RPA  
Runt Packet Accept. This bit  
forces the Am79C978 controller  
to accept runt packets (packets  
shorter than 64 bytes).  
CAUTION: Use this parameter  
with care. By lowering the IPG  
below the ISO/IEC 8802-3 stan-  
dard 96 bit times, the  
Am79C978 controller can inter-  
rupt normal network behavior.  
This bit is read accessible al-  
ways; write accessible only when  
STOP is set to 1. RPA is cleared  
by H_RESET or S_RESET and is  
not affected by STOP.  
These bits are read accessible al-  
ways. Write accessible when the  
STOP bit is set to 1. IPG is set to  
60h (96 Bit times) by H_RESET  
or S_RESET and is not affected  
by STOP.  
2-0  
RES  
Reserved locations. Written as  
zeros and read as undefined.  
CSR125: MAC Enhanced Configuration Control  
7-0  
IFS1  
InterFrameSpacingPart1. Chang-  
ing IFS1 allows the user to pro-  
gram the value of the InterFrame-  
Bit  
Name  
Description  
31-16 RES  
15-8 IPG  
Reserved locations. Written as  
zeros and read as undefined.  
SpacePart1  
timing.  
The  
Am79C978 controller sets the de-  
fault value at 60 bit times (3ch).  
See the subsection on Medium  
Allocation in the section Media  
Access Management for more  
details. The equation for setting  
IFS1 when IPG 96 bit times is:  
Inter Packet Gap. Changing IPG  
allows the user to program the  
Am79C978 controller for aggres-  
siveness on a network. By chang-  
ing the default value of 96 bit  
times (60h) the user can adjust  
the fairness or aggressiveness of  
the Am79C978 integrated MAC  
on the network. By programming  
a lower number of bit times other  
then the ISO/IEC 8802-3 stan-  
dard requires, the Am79C978  
controller will become more ag-  
gressive on the network. This ag-  
gressive nature will give rise to  
the Am79C978 controller possi-  
bly capturing the networkat  
times by forcing other less ag-  
gressive nodes to defer. By pro-  
gramming a larger number of bit  
times, the Am79C978 home net-  
working MAC will become less  
aggressive on the network and  
may defer more often than nor-  
mal. The performance of the  
Am79C978 controller may de-  
crease as the IPG value is in-  
creased from the default value.  
IFS1 = IPG - 36 bit times  
Note: Programming of the IPG  
should be done in nibble intervals  
instead of absolute bit times due  
to the MII. The decimal and hex  
values do not match due to de-  
lays in the part used to make up  
the final IPG.  
Changes should be added or  
subtracted from the provided hex  
value on a one-for-one basis.  
Due to changes in synchroniza-  
tion delays internally through dif-  
ferent network ports, the IFS1  
can be off by as much as +12 bit  
times.  
These bits are read accessible al-  
ways. Write accessible only when  
the SPND bit or the STOP bit is  
set to 1. IFS1 is set to 3ch (60 bit  
Note: Programming of the IPG  
should be done in nibble intervals  
instead of absolute bit times. The  
decimal and hex values do not  
times)  
by  
H_RESET  
or  
S_RESET and is not affected by  
STOP.  
144  
Am79C978