MU9C2485L-90TCC Просмотр технического описания (PDF) - MUSIC Semiconductors
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MU9C2485L-90TCC Datasheet PDF : 28 Pages
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WidePort LANCAM® Family
OPERATIONAL CHARACTERISTICS Continued
/E
/W
/CM
/E C
DQ15– 0
/E
DATA OUT
Figure 3: Read Cycle
/W
/CM
DQ15–0
/E
Figure 4: Write Cycle
COM PAR AND W RIT E
C YC L E
S TA TU S R EAD
C YC L E
ASS OC IAT ED D ATA
R EA D C YCL E
/CM
/W
DQ3 1 – 0
/EC
/M F
/M A, /M M
DA TA
DATA
DA TA
MATCH FLAG VALID
/M F FL A GS U P D A TE D
Figure 5: Cycle to Cycle Timing Example
of the Comparand Write cycle, assuming /EC is LOW at the
start of this cycle. Data writes and reads to the comparand,
mask registers or memory occur in one or two 32-bit cycles,
depending on the settings in the Segment Control register.
The Compare operation automatically occurs during Data
writes to the Comparand or mask registers when the
destination segment counter reaches the end count set in
the Segment Control register. If there was a match, the
second cycle reads status or associated data, depending
on the state of /CM. For cascaded devices, /EC needs to be
LOW at the start of the cycle prior to any cycle that requires
a locked daisy chain, such as a Status register or associated
data read after a match. If there is no match in Standard
mode, the output buffers stay HIGH-Z, and the daisy chain
must be unlocked by taking /EC HIGH during a NOP or
other non-functioning cycle, as indicated in Table 6a.
Figure 6 shows how the internal /EC timing holds the daisy
chain locking effect over into the next cycle. In the Enhanced
mode, this NOP is not needed before data or command
writes following a non-matching compare, as indicated by
Table 6b. A single-chip system does not require daisy-
chained match flag operation, hence /EC could be tied HIGH
and the /MA pin or flag in the Status register used instead
of /MF, allowing access to the device regardless of the
match condition.
The minimum timings for the /E control signal are given in
the Switching Characteristics section. Note that at minimum
timings the /E signal is non-symmetrical, and that different
cycle types have different timing requirements, as given in
Table 8.
13
Rev. 2
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