IDT75T43100S66BSI [IDT]
Telecom Circuit, CMOS, PBGA304;
| 型号： | IDT75T43100S66BSI |
| 厂家： | 
INTEGRATED DEVICE TECHNOLOGY |
| 描述： | Telecom Circuit, CMOS, PBGA304 电信 电信集成电路 |
| 文件： | 总8页 (文件大小：77K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
BasicTableMaintenceOperations
Application Note AN-271
Basic Table
Maintenance
Operations
Application
Note
AN-271
OffundamentalimportancetoanIPCisproperdatatablemainte-
Overview
nance:loading, deleting, andchangingthe various arrayvalues within
andcontrolledbytheIPC. TheIPCiscomprisedofbothadataarrayand
a maskarray. Additionally, there canbe anexternalSRAMtoholdthe
associateddatatothatofthedatastoredwithintheIPCentries.
Thisapplicationnotedetailstheproperexecutionofvarioustable
maintenance operations in the IDT75T43100 Internet Protocol
Co-Processor(IPC). Themaintenancefunctionsthatarepresentedare
theoperationsofadding,deletingandmodifyingentriesintheIPC’sData
and Mask arrays plus storing entries in an external SRAM.
The combination of the two arrays, data and mask, gives the IPC
thecapabilityofmaintainingaternarydatasetthatallowsforfast,
flexibleandefficientdatasearches. Ternarydataiscomprisedofthe
traditional binary data values of‘0’and‘1’ alongwitha thirdvalue of
‘X’ or don’t care. The IPC Data Array contains the ‘0’ and ‘1’ values
whiletheIPCMaskArraycontains thecare/don’tcareinformation.
During a lookup operation both arrays along with a Global Mask
Register(GMR)are usedtofinda matchtoa requesteddata set.
BackgroundInformation
TheIDT75T43100IPCisapowerfulandefficientperipheralthatcan
beusedwithallofthevariousNetworkProcessors(NPs),inadditionto
customASIClookupsolutions,forenhancingtheNP’sorASIC’spacket
processingcapabilities. TheprimaryapplicationoftheIPCistoassistNPs
and ASICs in achieving the high-speed data searching requirements
found in routers, the high layer packet processing environments of
switchesandapplicationsinvolvedintheconvergenceofvoice,data,and
video. TheIDT75T43100IPCcansupportasustainedbandwidthofat
least66millionsearchespersecond.
ToproperlymaintaindatavaluesintheIPCtheusermustcontrolthe
values intheDataandMaskArrays andadditionallythatofanoptional
external SRAM when used.
Nomenclature
Intheexamplesdetailedinthisapplicationnotethefollowingstructurewillbeusedtoillustratethediscussion:
CCLK cycle X theCCLKcyclethatthebus activityis takingplace(theCCLKis thelookupcycle)
BUS_NAME[X:Y]
• BUS_FIELD =
anidentificationofthebusbeingdiscussed
descriptionofadatafieldinBUS_NAME[X:Y]andoftheactionoccurringbythespecifiedfield
value
tX
theCLK2Xcyclethatthebusactivityistakingplace
At the bottom of every page that a bus diagram is presented, a bus diagram legend is also given. The bus diagram legend is as follows:
= Required Data Field
= OptionalParameters
= N/A
- datafieldthatthediscussionisfocusedonandisrequiredtobespecifiedasperthediscussion
- optionalparameters whose value maybe selectedbythe useras perthe user’s requirements
- datathatisnotapplicableforthediscussionordatabitsthatarereserved;typicallythesebitswill
have a value of ‘0’
FordetailedbusinformationpleaseseetheIDT75T43100datasheet.
MAY 2001
1
2002 Integrated Device Technology, Inc. All rights reserved. Product specifications subject to change without notice.
DSC-5332/00
BasicTableMaintanceOperations
Application Note AN-271
AddEntry
TheWritecommandwillbeadirectWriteinwhichtheaddressisexplicitly
presentedtotheIPC. AdditionalparametersoftheWritecommandthat
needto be specifiedare: 1)Access Type -todetermine whicharrayis
tobewrittento(DataArrayorMaskArray)and2)GMRSelect-anoptional
selectionastowhethertherewillbemaskingofanyoftheWritebits(no
maskingwillbeusedfortheAddEntryfunction).
TheAddEntryfunctionisusedtoloadvaluesintotheDataorMaskArrays
oftheIPC. Typicallythiswillbeusedforinitializationofthesetwoarrays
priortoanyusefulsearchesofIPCdata. Thisfunctionwouldalsobeused
forthenormalmaintenanceroutineoftableupdates. Toadddatatheuser
needstodoasingleoperation:theWritecommand.
TheWriteoperationisillustratedinthefollowingdiagram.
Add Entry - Perform Direct Write:
CCLK cycle 1:
INST[6:0]
6
4 3
0
GMR
Select
t0
INST
tbl 01
• INST = '0100', Write
6
4 3
0
SRR
Select
t1
INST
tbl 01a
• INST = '0100', Write
REQDATA[71:0]
71
34 33
26 25
24 23
22 21 20
D/I
17 16
15 14
1
0
GMR
Select
SRR
Select
Reserved
Device ID
Access Type
A14 A13 A13
A0 Res
tbl 02
• Access Type = ‘01’, Data Array; or ‘10’, Mask Array
• GMR Select = ‘11’, no mask
• D/I = ‘0’, Direct
• [A14:A0] = <address of entry to be stored>
(Note: A13 must be presented in both REQDATA[15] and REQDATA [14])
CCLK cycle 2:
REQDATA[71:0]
71
0
Write Data
tbl 03
Required Data Field
Optional Parameters
=
=
• Write Data = <Data Value to be Stored>
=
N/A
2
BasicTableMaintanceOperations
Application Note AN-271
Delete Entry
TheLookupcommandisissuedfirstandisshowninstep1oftheDelete
Entryexample. SelectionofaGMRspecifieswhichdatafieldsaretobe
included in the search of the Data Array and is specified during time t0.
Duringtimet1 theSRRisspecified. Thex72Lookupinstructionmustbe
presentduringbothtimest0andt1. Thereareseven(7)x72LookupGMRs
andeight(8)SRRs thatcanbeselectedforthis operation.
ThepurposeofaDeleteEntryfunctionistoremoveaspecificentry,that
hasbeenpreviouslystored,fromtheDataArray. Iftheaddressofthedata
isnot known,theusermustfirstsearchtheDataArrayforthedatavalue
needingtobedeletedandthenoncefound,removeitfromthearray. This
functionrequirestwooperations:aLookupcommandfollowedbyaWrite
command. IftheaddressisknownalookupisnotrequiredandaDirect
Writecommandcanbesimplyused.
FollowingtheLookupcommandistheindirectWritecommand. Theindirect
Writeis showninstep2.
The Lookup command returns the address of the specified data value
storedintheDataArray. TheWritecommand,inanindirectaddressing
mode, willthentake the resultingaddress fromthe Lookup, whichwas
storedinaselectedSearchResultRegister(SRR),topointtotheentry
toberemoved. Thus,throughuseofanIndirectWritetheuserisableto
immediately delete the entry, alleviating the need to read the returned
Lookupresultpriortoproceedingwithitsdeletion.
AnimportantfactorintheDeleteEntryfunctionisthetimingoftheWrite
commandtotheLookupcommand. Fortheproperexecutionofanindirect
addressing operation, the operation requires there to be a valid value
loadedintotheSRRpriortoitsuse.TheIDT75T43100requiresanindirect
write,usingtheresultsofapreviouslookuptospecifytheindirectaddress,
nottobecommandeduntilthe5th CCLKcycleoftheLookupcommand.
Delete Entry (step 1) Perform x72 Lookup:
CCLK cycle 1:
INST[6:0]
6
4 3
0
GMR
Select
t0
INST
tbl 04
• GMRSelect=Selectfield(s)toparse
• INST = ‘0010’, x72 Lookup
6
4 3
0
SRR
Select
t1
INST
tbl 05
• SRRSelect=SelectResultRegistertostoreLookupresult
• INST = ‘0010’, x72 Lookup
REQDATA[71:0]
71
0
Lookup D ata
tbl 06
• Lookup Data = Data entry to be deleted
=
=
Required Data Field
Optional Parameters
=
N/A
3
BasicTableMaintanceOperations
Application Note AN-271
Delete Entry (step 2) - Perform Indirect Write:
CCLK cycle 5:
INST[6:0]
6
4 3
0
GMR
Select
t0
INST
INST
tbl 07
• INST = ‘0100’, Write
6
4 3
0
SRR
Select
t1
tbl 07A
• INST = ‘0100’, Write
REQDATA[71:0]
71
34 33
26 25
24 23
22 21 20
D/I
17 16
15 14
1
0
GMR
Select
SRR
Select
Reserved
Device ID
Access Type
A14 A13 A13
A0 Res
tbl 09
• Access Type = ‘01’, Data Array
• GMRSelect=‘11’, nomask
• D/I = ‘1’, Indirect
• SSRSelect=SSRusedinLookupInstructionofstep1
CCLK cycle 6:
REQDATA[71:0]
71
0
Write Data
tbl 08
·WriteData=“000000000000000000”h
=
=
Required Data Field
Optional Parameters
=
N/A
4
BasicTableMaintanceOperations
Application Note AN-271
Modify Entry
t0 andt1. Thereareseven(7)x72LookupGMRsandeight(8)SRRsthat
canbeselectedforuse.
The Modify Entry function follows the same form as the Delete Entry
functionexcept,insteadofzeroing-outtheentireselecteddataentry,only
someofthedataischanged. Toaccomplishthistheuserwillneedtospecify
oneoftheIPC’swritecapableGMRsintheindirectWritecommand. This
GMRwillprovidethemasktodeterminewhichbitsofthe72-bitdataarray
aretobeaffectedbytheWritecommand.
FollowingtheLookupcommand, theModifyEntryfunctioniscompleted
with an indirect Write command. The indirect Write is shown in step 2.
DuringthissteptheGMRtousewiththeWriteisspecified.
The IPC has a total of 15 GMRs that can be used with its various (x72-
bit, x144-bit, x288-bit) Lookup commands to parse which data is to be
searched. Only3ofthesecanbeusedtomaskaWritecommand. These
are GMRs 10, 11 and 12.
Iftheaddressoftheentrytomodifyisnotknown,theusermustfirstsearch
thedataarrayforthedatavalueneedingtobemodifiedandthenonce
found, modifyit. Justas indeletinganentry, this functionrequires two
operations: a Lookup command followed by a Write command. If the
addressisknownaDirectWritecanbeusedtomodifytheentryinasingle
step.
(Note:The use ofa GMRis predicatedwiththe factthatthe GMRmust
have been previously loaded with the desired mask prior to its use.
Cautionmustalsobeexercisedwhenmultiplecontextsareaccessingthe
IPC’s GMR resources so that mask values do not become corrupted.)
TheLookupcommandisissuedfirstandisshowninstep1. Selectionof
aLookupGMR,INST[6:4]duringtimet0,specifieswhichdatafieldsare
tobeincludedinthesearchofthedataarray. Duringtimet1 theSRRis
specified. Thex72Lookupinstructionmustbepresentduringbothtimes
Again,thetimingoftheLookupcommandtoreturnaresultintothespecified
SRRtobeusedinanindirectwritemustbemaintained. TheIDT75T43100
requiresanindirectwrite,usingtheresultsofapreviouslookuptospecify
th
Modify Entry (step 1) Perform x72 Lookup:
theindirectaddress,nottobecommandeduntilthe5 CCLKcycleofthe
Lookupcommand.
CCLK cycle 1:
INST[6:0]
6
4 3
0
GMR
Select
t0
INST
tbl 10
• GMRSelect=Selectfield(s)toparse
• INST = ‘0010’, x72 Lookup
6
4 3
0
SRR
Select
t1
INST
tbl 10A
• SRRSelect=SelectResultRegistertostoreLookupresult
• INST = ‘0010’, x72 Lookup
REQDATA[71:0]
71
0
Lookup Data
tbl 06
=
=
Required Data Field
• Lookup Data = Data entry to be modified
Optional Parameters
N/A
=
5
BasicTableMaintanceOperations
Application Note AN-271
Modify Entry (step 2) - Perform Write:
CCLK cycle 5:
INST[6:0]
6
4 3
0
GMR
Select
t0
INST
INST
tbl 11
• INST = '0100', Write
6
4 3
0
SRR
Select
t1
tbl 11A
• INST = '0100', Write
REQDATA[71:0]
71
34 33
26 25
24 23
22 21 20
D/I
17 16
15 14
1
0
GMR
Select
SRR
Select
Reserved
Device ID
Access Type
A14 A13 A13
A0 Res
tbl 09
• Access Type = ‘01’, Data Array
• GMRSelect=Selectspecificdatafield(s)tomodifywiththeWrite
• D/I = ‘1’, Indirect
• SSRSelect=SSRusedinLookupInstructionofstep1
CCLK cycle 6:
REQDATA[71:0]
71
0
Write Data
tbl 08
• Write Data =<NewData Value>
=
=
Required Data Field
Optional Parameters
=
N/A
6
BasicTableMaintanceOperations
Application Note AN-271
Load External SRAM Entry
TheLoadExternalSRAMEntryfunctionisusedtoloadIPCassociated
dataintoanexternalSRAM. Thisfunctionwillbeusedduringinitialization
oftheassociateddatapriortosearchesofIPCdataaswellasattimesof
normaltablemaintenanceandupdates. ToloadexternalSRAMdatathe
userneedstodoasingleoperation:theWritecommand.
2) CE/OEandWEareoutputsignalsfromtheIPCthatdirectlydrivethe
appropriate pins of the external SRAM device (ZBT or PBSRAM).
3) DataflowintoandoutoftheexternalSRAMisnotthroughtheIPCbut
through the ASIC/FPGA. External SRAM accesses can be of
whateverdatawidthischosenfortheexternalSRAMtoASIC/FPGA
interface.
4) External SRAM addressing is never specified through indirect ad-
dressing.
5) AGMRcannotbeusedincombinationwithaWritecommandtoan
externalSRAMtomaskoffdatabits. (DatawrittentotheexternalSRAM
doesnotgothroughtheIPCandisnotabletobequalifiedbytheIPC.)
The Write command will be an external SRAM Write in which a 20-bit
addressisexplicitlypresentedtotheIPC. TheIPCwillthentakeandpass
thataddresstotheexternalSRAMalongwiththerequiredcontrolsignals.
OfkeyconsiderationinanexternalSRAMWriteisthecoordinationofthe
controlandaddresssignalswiththedatatotheexternalSRAM. Address
andcontrolsignalsarefromtheIPC. DataispresentedbytheASIC/FPGA.
WhentheIPCispresentedwiththeexternalSRAMWritecommand,the
IPCwilltransferthe20-bitaddressfromtheRequestDataBustotheIndex
BusandgeneratethenecessarySRAMcontrolsignals. Thedatawillneed
tobepresentedtotheSRAMbytheASIC/FPGAwhenrequired. (Refer
tothe IDT75T43100data sheetforthe sequencingandtimingrequire-
mentsofexternalSRAMaccesses.)
Also,pleasereviewtheIDT75T43100datasheetsectionsregardingthe
System Configuration Register (SCR) especially with respect to the
followingfields:
(SR) SRAM Type Bit
(LS)LastSRAMBit
(PD)Pipeline DelayBits
(IPC Grp) IPC Group Bits
UnderstandingtheexternalSRAMinterface:
TheexternalSRAMWriteoperationisillustratedonthenextpageinthe
AddExternal SRAM Entry example.
1) AddressesforexternalSRAMaccessesareformatteddifferently
thanforinternalIPCaccesses. Whenaccessinganexternal
SRAM the IPC is configured in a Bypass Mode in which the IPC
passes a20-bitaddress fromtheRequestDataBus totheIndex
Bus. TheformatoftheREQDATABusisdifferentthanthatofan
internalIPCaccess. (See IDT75T43100data sheet.)
7
BasicTableMaintanceOperations
Application Note AN-271
Add External SRAM Entry - Perform external SRAM Write:
CCLK cycle 1:
INST[6:0]
6
4
3
0
GMR
Se le ct
t0
INST
INST
tbl 01
• INST = '0100', Write
6
4
3
0
SRR
Se le ct
t1
tb l 01 a
• INST = '0100', Write
REQDATA[71:0]
71
34 33
26 25
24 23
21 20
A19
16
15 14
0
Reserved
Device ID
Access Type
Reserved
A15 A14 A14
A0
tbl 12
• Access Type = ‘11’, external SRAM
• [A19:A0] = <address of entry to be stored>
(Note: A14 must be presented in both REQDATA[15]
and REQDATA [14])
IPC Bypass Mode
Bus Transfer
CCLK cycle 6:
INDX[19:0] is driven.
19
15 14
0
A15
A0
A19
A14
tbl 13
• Address on the REQDATA bus is transferred to the INDX bus.
REQDATA[20:16],[14:0] INDX[19:15],[14:0]
SRAM Control Signals CE/OE and WE are generated.
CCLK cycle 8:
=
=
Required Data Field
Optional Parameters
=
N/A
Write Data is presentedtothe externalSRAMfromthe ASIC/FPGAonthe ZBTData Bus.
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8
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