MU9C8K64-50TDC データシートの表示（PDF） - Music Semiconductors

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MU9C8K64-50TDC

MU9C Routing Coprocessor (RCP) Family

Music Semiconductors 

MU9C Binary Routing Coprocessor (RCP) Family

Register Descriptions

'1'

'0'

+3.3V

/MI

/FI

/MF

MU9C

/FF

/MM

Highest Priority

/MI

/FI

/MF

MU9C

/FF

/MM

/MI

/FI

MU9C

/MF

/FF

/MM

Lowest Priority

Match Full

Multiple-match

Figure 4: Vertically Cascading MU9C RCPs

Full Cascading

The Full flag is set LOW in a particular MU9C RCP if the

/FI line is LOW, and that device is full. During a Write

cycle, the Full flag will not change until /E goes HIGH

during that cycle. When the /FI line is HIGH, one or more

locations are free in the higher-priority devices; therefore,

when the /FI line is HIGH, whether or not that particular

device is full, its /FF output will remain HIGH. This

method allows the Full Flag daisy chain to recognize

non-contiguous empty locations throughout the entire

MU9C RCP system.

The daisy chain gives System Full indication. When the

device at the end of the chain has its /FF output LOW, the

entire CAM system is full. The first device in the daisy

chain has its /FI line tied LOW to ensure data can be

written into the system.

The daisy chain also controls Write at Next Free Address

cycles as well as Read Next Free Address cycles so that

they work globally across the system, and not just locally in

a specific device. Only the device in which the /FI line is

LOW, and which is not full, will respond to the Write cycle.

Therefore, deletions and insertions can be made in the

memory, without the need to keep track of empty locations.

Match Cascading

The Match flag /MF will be LOW in a particular device

within a vertically cascaded system when its /MI input is

LOW, or when there is a match in that device. During a

Comparison cycle, the Match flag will not change until /E

goes HIGH during that cycle. When the /MI line is LOW,

one or more locations in higher-priority devices have a

match; when the /MI line is LOW, the /MF output will be

forced LOW. This method allows the Match Flag daisy

chain to respond to and prioritize matches throughout the

entire MU9C RCP system.

The daisy chaining gives a System Match indication. When

the device at the end of the daisy chain has its /MF output

LOW, there is a match within the MU9C system. The first

device in the daisy chain has its /MI input tied HIGH.

The daisy chain also controls access to the device by

controlling the outputs during a Read Highest-Priority

Match data, or Read Status register, onto the DQ31–0 lines.

The device must be selected with either /CS1, or /CS2, or

the Data Select register. After a Comparison or Read/Write

at Highest-Priority Match Address cycle, only the device

whose /MI line is HIGH, and which has a valid match, will

drive data onto DQ31–0 or onto PA:AA bus; any device

that has its /MI line set LOW will have its outputs in their

high-impedance state, even if it has a valid match.

Therefore, Reads from and Writes to the Highest-Priority

Matching address operate over the entire system; only the

device in which the /MI line is HIGH and that has a match

will respond to the cycle. This scheme automatically

prioritizes a system of vertically cascaded devices, the

highest up in the chain has the highest-priority. Note

however, that cycles that do not access highest-priority

match data or the Status register will operate without regard

to the state of the Match daisy chain.

Multiple Match Flag Daisy Chain

The Multiple Match flag, /MM, is an open-drain output, and

will be pulled LOW by a particular device when its /MI

input is HIGH and there is more than one match within the

device, or when the /MI input is LOW and there is one

match within the device. During a Comparison cycle, the

Multiple Match flag will not change until /E goes HIGH

during that cycle. This wired-OR output provides system

level indication of the multiple match condition within a

vertically cascaded system of MU9C RCPs.

Match Flag Timing Overhead

There is a propagation delay for the match results to ripple

down through the daisy chain. All the MU9C RCPs

within the system execute a Comparison cycle in parallel,

so the local results are available at the end of a

Comparison cycle. The local Match flags do not change

during a Comparison cycle until /E goes HIGH. The

logical combination of the results then propagates down

12

Rev. 6

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