参数资料
型号: IDT72V51246L6BB8
厂商: IDT, Integrated Device Technology Inc
文件页数: 16/56页
文件大小: 0K
描述: IC FLOW CTRL MULTI QUEUE 256-BGA
标准包装: 1,000
类型: 多队列流量控制
安装类型: 表面贴装
封装/外壳: 256-BBGA
供应商设备封装: 256-BGA(17x17)
包装: 带卷 (TR)
其它名称: 72V51246L6BB8
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COMMERCIALANDINDUSTRIAL
TEMPERATURERANGES
IDT72V51236/72V51246/72V51256 3.3V, MULTI-QUEUE FLOW-CONTROL DEVICES
(4 QUEUES) 36 BIT WIDE CONFIGURATION 589,824, 1,179,648 and 2,359,296 bits
for the new queue one cycle ahead of the WCLK rising edge that data can be
written into the new queue. That is, a new queue can be selected on the write
port via the WRADD bus, WADEN enable and a rising edge of WCLK. On the
nextrisingedgeofWCLK,the
FFflagoutputwillshowthefullstatusofthenewly
selected queue. On the second rising edge of WCLK following the queue
selection, data can be written into the newly selected queue provided that data
and enable setup & hold times are met.
Note, the
FF flag will provide status of a newly selected queue one WCLK
cycleafterqueueselection,whichisonecyclebeforedatacanbewrittentothat
queue.Thispreventstheuserfromwritingdatatoaqueuethatisfull,(assuming
that a queue switch has been made to a queue that is actually full).
The
FFflagissynchronoustotheWCLKandalltransitionsoftheFFflagoccur
basedonarisingedgeofWCLK.Internallythemulti-queuedevicemonitorsand
keeps a record of the full status for all queues. It is possible that the status of a
FFflagmaybechanginginternallyeventhoughthatflagisnottheactivequeue
flag (selected on the write port). A queue selected on the read port may
experience a change of its internal full flag status based on read operations.
See Figure 9, Write Queue Select, Write Operation and Full Flag Operation
and Figure 11, Full Flag Timing in Expansion Mode for timing information.
EXPANSION MODE - FULL FLAG OPERATION
When multi-queue devices are connected in Expansion mode the
FF flags
of all devices should be connected together, such that a system controller
monitoring and managing the multi-queue devices write port only looks at a
single
FF flag (as opposed to a discrete FF flag for each device). This FF flag
is only pertinent to the queue being selected for write operations at that time.
Remember, that when in expansion mode only one multi-queue device can be
written to at any moment in time, thus the
FF flag provides status of the active
queue on the write port.
Thisconnectionofflagoutputstocreateasingleflagrequiresthatthe
FFflag
output have a High-Impedance capability, such that when a queue selection is
made only a single device drives the
FF flag bus and all other FF flag outputs
connected to the
FF flagbusareplacedintoHigh-Impedance.Theuserdoes
not have to select this High-Impedance state, a given multi-queue flow-control
device will automatically place its
FF flag output into High-Impedance when
none of its queues are selected for write operations.
Whenqueueswithinasingledeviceareselectedforwriteoperations,the
FF
flag output of that device will maintain control of the
FF flag bus. ItsFFflagwill
simplyupdatebetweenqueueswitchestoshowtherespectivequeuefullstatus.
Themulti-queuedeviceplacesits
FFflagoutputintoHigh-Impedancebased
onthe3bitIDcodefoundinthe3mostsignificantbitsofthewritequeueaddress
bus,WRADD.Ifthe3mostsignificantbitsofWRADDmatchthe3bitIDcodesetup
on the static inputs, ID0, ID1 and ID2 then the
FF flag output of the respective
device will be in a Low-Impedance state. If they do not match, then the
FFflag
output of the respective device will be in a High-Impedance state. See Figure
11, Full Flag Timing in Expansion Mode for details of flag operation, including
when more than one device is connected in expansion.
OUTPUT VALID FLAG OPERATION
The multi-queue flow-control device provides a single Output Valid flag
output,
OV.TheOVprovidesanemptystatusordataoutputvalidstatusforthe
data word currently available on the output register of the read port. The rising
edgeofanRCLKcyclethatplacesnewdataontotheoutputregisteroftheread
port, also updates the
OV flag to show whether or not that new data word is
actually valid. Internally the multi-queue flow-control monitors and maintains a
statusoftheemptyconditionofallqueueswithinit,howeveronlythequeuethat
is selected for read operations has its output valid (empty) status output to the
OV flag, giving a valid status for the word being read at that time.
The nature of the first word fall through operation means that when the last
data word is read from a selected queue, the
OV flag will go HIGH on the next
enabled read, that is, on the next rising edge of RCLK while
REN is LOW.
Whenqueueswitchesarebeingmadeonthereadport,the
OVflagwillswitch
toshowstatusofthenewqueueinlinewiththedataoutputfromthenewqueue.
When a queue selection is made the first data from that queue will appear on
the Qout data outputs 2 RCLK cycles later, the
OVwillchangestatetoindicate
validity of the data from the newly selected queue on this 2nd RCLK cycle also.
The previous cycles will continue to output data from the previous queue and
the
OVflagwillindicatethestatusofthoseoutputs.Again,the OV flagalways
indicates status for the data currently present on the output register.
The
OVflagissynchronoustotheRCLKandalltransitionsoftheOVflagoccur
basedonarisingedgeofRCLK.Internallythemulti-queuedevicemonitorsand
keepsarecordoftheoutputvalid(empty)statusforallqueues.Itispossiblethat
thestatusofan
OVflagmaybechanginginternallyeventhoughthatrespective
flag is not the active queue flag (selected on the read port). A queue selected
on the write port may experience a change of its internal
OVflagstatusbased
on write operations, that is, data may be written into that queue causing it to
become “not empty”.
See Figure 12, Read Queue Select, Read Operation and Figure 13, Output
Valid Flag Timing for details of the timing.
EXPANSION MODE – OUTPUT VALID FLAG OPERATION
When multi-queue devices are connected in Expansion mode, the
OVflags
of all devices should be connected together, such that a system controller
monitoring and managing the multi-queue devices read port only looks at a
single
OVflag(asopposedtoadiscreteOVflagforeachdevice).ThisOVflag
is only pertinent to the queue being selected for read operations at that time.
Remember, that when in expansion mode only one multi-queue device can be
read from at any moment in time, thus the
OVflagprovidesstatusoftheactive
queue on the read port.
Thisconnectionofflagoutputstocreateasingleflagrequiresthatthe
OVflag
output have a High-Impedance capability, such that when a queue selection is
made only a single device drives the
OV flagbusandallotherOVflagoutputs
connected to the
OV flagbusareplacedintoHigh-Impedance.Theuserdoes
not have to select this High-Impedance state, a given multi-queue flow-control
device will automatically place its
OV flag output into High-Impedance when
none of its queues are selected for read operations.
Whenqueueswithinasingledeviceareselectedforreadoperations,the
OV
flag output of that device will maintain control of the
OVflagbus.ItsOVflagwill
simply update between queue switches to show the respective queue output
validstatus.
Themulti-queuedeviceplacesits
OVflagoutputintoHigh-Impedancebased
onthe3bitIDcodefoundinthe3mostsignificantbitsofthereadqueueaddress
bus,RDADD.Ifthe3mostsignificantbitsofRDADDmatchthe3bitIDcodesetup
on the static inputs, ID0, ID1 and ID2 then the
OVflagoutputoftherespective
device will be in a Low-Impedance state. If they do not match, then the
OVflag
output of the respective device will be in a High-Impedance state. See Figure
13, Output Valid Flag Timing for details of flag operation, including when more
than one device is connected in expansion.
ALMOST FULL FLAG
As previously mentioned the multi-queue flow-control device provides a
singleProgrammableAlmostFullflagoutput,
PAF.ThePAFflagoutputprovides
astatusofthealmostfullconditionfortheactivequeuecurrentlyselectedonthe
write port for write operations. Internally the multi-queue flow-control device
monitors and maintains a status of the almost full condition of all queues within
it, however only the queue that is selected for write operations has its full status
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