MU9C4320L-12DC データシートの表示（PDF） - Music Semiconductors

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MU9C4320L-12DC

ATMCAM

Music Semiconductors 

Operational Characteristics

MU9C4320L ATMCAM

Software Control

For optimum performance, the ATMCAM is controlled

through the AC11–0 lines, allowing data transactions

through the DQ31–0 lines during a control cycle. In cases

where the overhead of a separate data load cycle can be

accommodated, the ATMCAM can be operated through

the Instruction register.

Control through the Instruction register is selected by the

FR27–26 bits of the Configuration register being set

HIGH. Under this circumstance, the AC11–0 lines are not

used, instead the instruction is loaded from the DQ11–0

lines into the Instruction register during a Write cycle with

the /AV line HIGH. The instructions are directly

analogous to the control states for any operation that does

not involve data transfer on the DQ31–0 lines, in which

case the instruction is executed during the same cycle as

the instruction is loaded. To distinguish between Read and

Write control states, DQ12 is used to indicate which type

of instruction should be executed. When DQ12 is LOW at

the beginning of the cycle, the instruction executed is the

Write Cycle instruction (/W = LOW when control state is

conveyed on AC11–0); when DQ12 is HIGH at the

beginning of the cycle, the instruction executed is the

Read Cycle instruction (/W = HIGH when control state is

conveyed on AC11–0).

When the instruction calls for data to be written or read

from the DQ31–0 lines, the instruction is loaded into the

Instruction register during the cycle, and the next Data

Read or Write cycle with /AV LOW executes the

instruction using the DQ31–0 bus for the data transaction.

The instruction is persistent; i.e., if no other instruction is

loaded into the Instruction Register, subsequent data

transactions with the /AV line LOW will be executed

according to the instruction currently loaded in the

Instruction register. When there is a data access to a

memory location on DQ31–0 associated with the

instruction, the /VB line carries the validity of that

location.

Instructions that involve data transactions on DQ31–0, and

are therefore executed on a subsequent Read or Write

cycle with the /AV line LOW, are all Read/Write Memory

and Read/Write Register instructions, Read Validity, Write

DQ3–0 to PA in Configuration register of Highest-Priority

Empty device, and Set /FF. All other instructions are

executed in a single cycle with the state of DQ12 being

interpreted as the state of the /W line during the equivalent

hardware control state. A Read cycle with /AV HIGH

accesses the Status register.

Active Address Interface PA3–0:AA11–0

The Active Address interface PA3–0:AA11–0 carries the

currently active address. The address source depends on

the most recent control state that caused it to change. The

possible address sources that are output on

PA3–0:AA11–0 are: Highest-Priority CAM Match

address, VP Table Match address, Next Free address,

CAM Read address, CAM Write address, VP Table Read

address, and VP Table Write address.

PA3–0:AA11–0 After a Comparison Cycle

After a Comparison cycle, or access to the

Highest-Priority address, the PA3–0:AA11–0 lines carry

one of three possible results:

• The CAM Match address if the Comparison cycle

resulted in a match in the CAM. Only the device

containing the highest-priority match enables its

PA3–0:AA11–0 lines. All other devices with either no

match or a lower-priority match, as indicated by the

Match Flag daisy chain, keep their PA3–0:AA11–0

lines in high impedance regardless of the state of their

/OE inputs.

• The VP Table Match address if the Comparison cycle

resulted in a mismatch in the CAM but a match in the

VP Table. Only the lowest-priority device, as

indicated by bit FR25 in the Configuration register,

enables its PA3–0:AA11–0 lines. All other devices

keep their PA3–0:AA11–0 lines in high impedance

regardless of the state of their /OE inputs.

• All 1s if there was no match in either CAM or VP

Table, or there was no match in the CAM and the VP

Table was disabled by Configuration register bit FR24

being HIGH. The lowest-priority device, as indicated

by bit FR25 in the Configuration register, enables its

PA3–0:AA11–0 lines and provides the source of all

1s. All other devices will keep their PA3–0:AA11–0

lines in high impedance regardless of the state of their

/OE inputs.

Rev. 3

11

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