mh2080 Music Semiconductors, Inc., mh2080 Datasheet - Page 11

• Manufacturer Part Number: mh2080
• Description: Hla Packaged Asynchronous Data Recognition And Recall Processor
• Manufacturer: Music Semiconductors, Inc.

Active Address Interface PA:AA Bus
The Active Address interface PA:AA bus 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 PA:AA bus are:
Highest-Priority Match address, Next Free address, Read
address, and Write address.
PA:AA Bus After a Comparison Cycle
After
Highest-Priority address, the PA:AA bus carries one of the
following two possible results:
•
•
PA:AA Bus After a Write at Next Free Address Cycle
After a Write at Next Free Address cycle the PA:AA
carries the address that was written to during that cycle.
Only the device in which the write occurred enables its
PA:AA bus. All other devices keep their PA:AA bus in
high-impedance regardless of the state of their /OE inputs.
In the event that the system was full prior to the Write at
Next Free Address cycle being executed, so that the write
operation was suppressed, the PA:AA carries all 1s. The
lowest-priority device, as indicated by bit FR25 in the
Configuration register, enables its PA:AA bus and
provides the source of all 1s. All other devices keep their
PA:AA in high-impedance regardless of the state of their
/OE inputs.
PA:AA Bus After a Random Access Read or Write to
the CAM
After a random Read or Write cycle to the MU9C, the
PA:AA bus carries the address that was accessed during
that cycle. Only the device in which the access occurred
enables its PA:AA bus. All other devices keep their
PA:AA bus in high-impedance regardless of the state of
their /OE inputs. Note that the access to the PA:AA bus
differs in this respect from the operation of the Status
register, which is accessible in any selected device under
this particular circumstance.
Rev. 1.1a
The Match address if the Comparison cycle resulted
in a match in the MU9C. Only the device containing
the highest-priority match enables its PA:AA bus. All
other devices with either no match or a lower-priority
match, as indicated by the Match Flag daisy chain,
keep their PA:AA bus in high-impedance regardless
of the state of their /OE inputs.
All 1s if there was no match in the MU9C. The
lowest-priority device, as indicated by bit FR25 in the
Configuration register, enables its PA:AA bus and
provides the source of all 1s. All other devices will
keep their PA:AA bus in high-impedance regardless
of the state of their /OE inputs.
a
Comparison
cycle,
or
access
to
the
11
In the event that the Write cycle was broadcast to multiple
devices, all devices that have their /OE lines held LOW
will enable their PA:AA bus. Under this circumstance, it is
up to the system designer to ensure that only one /OE line
is driven LOW to prevent bus contention on the PA:AA
bus.
PA:AA Bus Conditions of Operation
•
•
•
PA:AA Bus and the Match Flags
The Match flags /MF and /MM reflect the results of the
most recent Comparison cycle. During a Comparison
cycle, they do not change until after /E has gone HIGH
after which they are free to change combinatorially; their
state is not latched when /E is LOW. This condition allows
some pipelining to occur and is useful in systems with
long daisy chains. A Comparison cycle can be followed by
another cycle that does not affect the PA:AA bus before
the daisy chain is resolved. For example:
The WRL CR control state can be executed before the
daisy chain has resolved device prioritization after the
CMP CR control state. The /OE then is asserted at a
suitable time, depending on the length of the daisy chain.
The Match address of the highest-priority responding
device then is driven onto the PA:AA bus.
The /MF, /MM lines continue to indicate the results of the
most recent match, even when the PA:AA bus carries an
address other than the Match address. This condition
allows rapid return to the Match address value on the
PA:AA bus lines through a RDL[HPM] cycle, without the
daisy
prioritization.
During a control state that does not have any effect on
the device address, such as a Write Register cycle, the
PA:AA bus remains unchanged. In other words, the
state of the PA:AA bus persists until another cycle
causes it to change.
When enabled by /OE being LOW, the PA:AA bus is
only free to change while /E is HIGH. When /E goes
LOW the PA:AA bus is latched.
The PA:AA bus is enabled when /OE is LOW
provided that the previous cycle causes them to be
active. When /OE is HIGH, the PA:AA bus is in
high-impedance. Note that /OE is asynchronous with
respect to /E, and is independent of Chip Select from
either /CS1, /CS2, or through the Device Select
register, except in the case of non-broadcast random
Read and Write cycles to the MU9C.
chain
having
CMP CR
WR CR
to
re-resolve
device-level