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MU9C4480L-90DC 参数 Datasheet PDF下载

MU9C4480L-90DC图片预览
型号: MU9C4480L-90DC
PDF下载: 下载PDF文件 查看货源
内容描述: LANCAM A / L系列 [LANCAM A/L series]
分类和应用: 局域网
文件页数/大小: 32 页 / 332 K
品牌: MUSIC [ MUSIC SEMICONDUCTORS ]
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Operational Characteristics  
LANCAM A/L series (not recommended for new designs)  
Compare Operations  
second, to provide a system wide match flag; third, to lock  
out all devices except the one with the Highest-Priority  
match for instructions such as Status reads after a match.  
The Match flag logic causes only the highest-priority  
device to operate on its Highest-Priority Match location  
while devices with lower-priority matches ignore  
Highest-Priority Match operations. The lock-out feature is  
enabled by the match flag cascading and the use of the /EC  
control signal, as shown in Table 4.  
During a Compare operation, the data in the Comparand  
register is compared to all locations in the Memory array  
simultaneously. Any Mask register used during compares  
must be selected beforehand in the Control register. There  
are two ways compares are initiated: Automatic compare  
and Forced compare.  
Automatic compares perform a compare of the contents of  
the Comparand register against Memory locations that are  
tagged as “Valid,” and occur whenever the following  
happens:  
The ripple delay of the flags when connected in a daisy  
chain requires the extension of the /E HIGH time until the  
logic in all devices has settled out. In a string of “n”  
devices, the /E HIGH time should be greater than  
The Destination Segment counter in the Segment  
Control register reaches its end limit during writes to  
the Comparand or Mask registers.  
tEHMFV + (n-2)· tMIVMFV  
After a command write of a TCO CT is executed  
(except for a software reset), so that a compare is  
executed with the new settings of the Control register.  
If the last device’s Match flag is required by external logic  
or a state machine before the start of the next CAM cycle,  
one additional tMIVMFV should be added to the /E HIGH  
time along with the setup time and delays for the external  
logic.  
Forced compares are initiated by CMP instructions using  
one of the four validity conditions: V, R, S, and E. The  
forced compare against “Empty” locations automatically  
masks all 64 bits of data to find all locations with the  
validity bits set to “Empty,” while the other forced  
compares are only masked as selected in the Control  
register.  
/E  
/EC  
Vertical Cascading  
/EC (INT)  
/MF  
LANCAMs can be vertically cascaded to increase system  
depth. Through the use of flag daisy-chaining, multiple  
devices respond as an integrated system. The flag daisy  
chain allows all commands to be issued globally, with a  
response only in the device containing the Highest-Priority  
Matching or Next Free location. When connected in a  
daisy chain, the last device’s Full flag and Match flag  
accurately report the condition for the whole string. A  
system in which LANCAMs are vertically cascaded using  
daisy-chaining of the flags is shown in Figure 3 on page 7.  
Figure 9: /EC (Int) Timing Diagram  
Locked Daisy Chain  
In a locked daisy chain, the highest-priority device is the  
one with /MI HIGH and /MF LOW. In Standard mode,  
only this device responds to command and data reads and  
writes, until the daisy chain has been unlocked by taking  
/EC HIGH. This allows reading the associated data field  
from only the Highest-Priority Match location anywhere  
in a string of devices, or the Match address from the Status  
register of the device with the match. It also permits  
updating the entry stored at the Highest-Priority Match  
location. In Enhanced mode, devices are enabled to  
respond to some command and data writes, as noted in  
Table 4 on page 12, but not command and data reads.  
To operate the daisy chain, the Device Select registers are  
set to FFFFH to enable all devices to execute Command  
Write and Data Write cycles. In normal operation, read  
cycles are enabled from the device with the  
Highest-Priority match by locking the daisy chain (see the  
Locked Daisy Chain section). An individual device in the  
chain may be targeted for a read or write operation by  
temporarily setting the Device Select registers to the Page  
address of the target device. Setting the Device Select  
registers back to FFFFH restores the operation of the  
entire daisy chain.  
Table 4 (Standard and Enhanced modes) show when a  
device responds to reads or writes and when does not,  
based on the state of /EC(int), the internal match  
condition, and other control inputs. /EC is latched by the  
falling edge of /E. /EC(int) is registered from the latched  
/EC signal off the rising edge of /E, so it controls what  
happens in the next cycle, as shown in Figure 9 on page  
Match Flag Cascading  
The Match Flag daisy chain cascading has three purposes:  
first, to allow operations on Highest-Priority Match  
addresses to be issued globally over the whole string;  
Rev. 1  
15  
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