Freescale Semiconductor, Inc.
match bit as defined by the mask register is ignored for this
operation. The operation of the MCM69C432 guarantees
that no more than one matching entry can exist in the table,
unless they were accidently loaded using fast–entry mode.
This must be avoided by the user, as the results of subse-
quent matches and deletes will be undefined.
interrupt is generated if enabled by bit 4 of the interrupt
register.
If this mode is used to enter data, the initialize–table opera-
tion must be executed before matching operations can
begin. The entry–mode bit and the table–initialized bit of the
flag register are cleared by this operation.
Example: I/O Register 0 =
I/O Register 1 =
I/O Register 2 =
I/O Register 3 =
Concatenated value =
302016
000016
543A16
FE5516
FE55543A0000302016
BUFFERED–ENTRY MODE
This instruction is used to enter the buffered–entry mode.
When the MCM69C432 is in this mode, insert–value and de-
lete–value operations utilize the entry queue. This mode can
.
Of the high–order 32 bits, the rightmost 30 bits
operation, if all entries are made in C this mode. Note that if
N –entry modes have been
,I
the MCM69C432 will delete an entry, if it exists,
used to input data, none R the entries are available for
O
which has a value of 3E55543A16 in bits 61 – 32.
CT
U
ND
the CAM, a O corresponding delete–entry in the queue, and a
IC
M
later insert–entry in the queue (all with the same match data),
the E queued insert–entry will return a match value.
S
bits that have a 0 in the corresponding bit of the global–mask LE RETURN ENTRY COUNT
register are used to find a matching entry in the CAM table. C If A
E
flag register is set. In addition, the matching entry is E
R
I/O registers 0 – 3, with bit 15 of register 3 as the F most signifi-
Y
cant bit, and bit 0 of register 0 as the least B significant bit
cleared. An interrupt is generated VE
I register, when the operation if
regardless of the result,
RC
A
forming matches. A 1 indicates that a bit should be ignored in
the match operation, while a 0 indicates that a bit should be
used in the match operation.
When this operation is executed, the contents of I/O regis-
ters 0 – 3 are concatenated, with bit 15 of register 3 as the
most significant bit, and bit 0 of register 0 as the least signifi-
Global–Mask Register = C0000000FFFFFFFF16 be entered at any time. Table entries are available for match
operations immediately, without running the initialize–table
are cared by the global–mask register. Therefore,
both the buffered–entry and fast
of
matching until the initialize–table operation is executed. Con-
CHECK FOR VALUE flicting table and queue values are resolved in favor of the
latest entry in the queue. For example, if there is an entry in
This instruction checks for a matching value in the CAM
table via the control port. The contents of I/O registers 0 – 3
are concatenated, with bit 15 of register 3 as the most signifi-
cant bit, and bit 0 of register 0 as the least significant bit. The
of
such an entry is found, the last–match–successful bit S the This operation is used to determine the number of valid
written to entries in the MCM69C432. The value is returned in I/O reg-
ister 0, and reflects the sum of the number of valid entries in
the CAM table and the inserts in the entry queue.
D
If no match is found, the last–match–successful bit is
SET GLOBAL–MASK REGISTER
H
enabled by bit 2 of the interrupt This operation is used to indicate the bits to be used in per-
has been completed. The operation of the MCM69C432
guarantees that no more than one matching entry can exist
in the table. If uninterrupted by match port activity, the check
for value instruction will finish in 8 clock cycles. NOTE: If both
the control and matching ports are utilized simultaneously,
see the Simultaneous Port Operations section.
INITIALIZE TABLE
If fast–entry mode has been used to load the CAM table,
the initialize–table operation must be used to establish the
needed relationships and linkages between the entries in the
table before matching can proceed. Upon completion, this
operation sets the table–initialized bit in the flag register, and
generates an interrupt if enabled by bit 3 of the interrupt reg-
ister. It also sets the buffered–entry mode bit in the flag regis-
ter. This operation makes the programming model’s registers
read–only for up to 80 ms after the acknowledgment of the
op code write cycle.
FAST–ENTRY MODE
This instruction is used to enter the fast –entry mode.
When the MCM69C432 is in this mode, insert–value opera-
tions bypass the entry queue and write new table entries
directly to the CAM table. The fast–entry mode can only be
entered while the entry queue is empty, as reflected by the
queue–empty flag being set (bit 4 of the flag register.) If this
operation is attempted while the entry queue is not empty,
the value FFFA16 is written to the error code register, the
error–condition flag (bit 7) is set in the flag register, and an
cant bit. The resulting 64–bit value is written to the global–
mask register.
This operation should be executed before entering re-
quired values into the CAM table. Otherwise, the initialize–
table instruction must be executed if the global –mask
register is changed after data is loaded into the CAM.
SET ALMOST–FULL POINT
This operation is used to define the “almost–full” condition
in the CAM table. The 14 low–order bits of I/O register 0 are
copied to the almost–full–point register. If an entry is added
to the MCM69C432 (via the insert–value operation) that
causes the valid–entry count to equal the almost–full point,
then bit 8 of the flag register is set, and an interrupt is gener-
ated if enabled by bit 5 of the interrupt register. The value of
the almost–full register can be changed dynamically during
match operations. For example, it could first be set to 8192 to
generate an interrupt when the table is half full. When that
point is reached, the register could be reprogrammed to
12,288 to provide warning that the table has become three–
quarters full. The almost –full interrupt is generated, if
enabled, based on the number of entries in the CAM table.
Entries in the queue are not included in the count.
MOTOROLA FAST SRAM
For More Information On This Product,
Go to: www.freescale.com
MCM69C432 ? SCM69C432
9
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