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參數(shù)資料
| 型號： | 70V25S15PFG |
| 廠商： | INTEGRATED DEVICE TECHNOLOGY INC |
| 元件分類： | SRAM |
| 英文描述： | 8K X 16 DUAL-PORT SRAM, 15 ns, PQFP100 |
| 封裝： | 14 X 14 MM, 1.40 MM HEIGHT, GREEN, PLASTIC, TQFP-100 |
| 文件頁數(shù)： | 15/25頁 |
| 文件大小： | 211K |
| 代理商： | 70V25S15PFG |
6.42
IDT70V35/34S/L
(IDT70V25/24S/L)
High-Speed 3.3V 8/4K x 18 (8/4K x 16) Dual-Port Static RAM
Industrial and Commercial Temperature Ranges
22
Figure 3. Busy and chip enable routing for both width and depth expansion with IDT70V35/34 (IDT70V25/24) SRAMs.
not desirable, the
BUSYlogiccanbedisabledbyplacingthepartinslave
mode with the M/
Spin.OnceinslavemodetheBUSYpinoperatessolely
as a write inhibit input pin. Normal operation can be programmed by tying
the
BUSY pins HIGH. If desired, unintended write operations can be
prevented to a port by tying the
BUSY pin for that port LOW.
The
BUSY outputs on the IDT70V35/34 (IDT70V25/24) SRAM in
master mode, are push-pull type outputs and do not require pull up
resistors to operate. If these SRAMs are being expanded in depth, then
the
BUSYindicationfortheresultingarrayrequirestheuseofanexternal
AND gate.
Width Expansion with Busy Logic
Master/Slave Arrays
When expanding an IDT70V35/34 (IDT70V25/24) SRAM array in
widthwhileusing
BUSYlogic,onemasterpartisusedtodecidewhichside
of the SRAM array will receive a
BUSY indication, and to output that
indication. Any number of slaves to be addressed in the same address
range as the master, use the
BUSY signal as a write inhibit signal. Thus
on the IDT70V35/34 (IDT70V25/24) SRAM the
BUSY pin is an output if
the part is used as a master (M/
Spin = VIH), andthe BUSYpinisaninput
if the part used as a slave (M/
S pin = VIL) as shown in Figure 3.
Iftwoormoremasterpartswereusedwhenexpandinginwidth,asplit
decision could result with one master indicating
BUSYononesideofthe
array and another master indicating
BUSYononeothersideofthearray.
This would inhibit the write operations from one port for part of a word and
inhibitthewriteoperationsfromtheotherportfortheotherpartoftheword.
The
BUSY arbitration, on a master, is based on the chip enable and
address signals only. It ignores whether an access is a read or write. In
a master/slave array, both address and chip enable must be valid long
enoughfora
BUSYflagtobeoutputfromthemasterbeforetheactualwrite
pulsecanbeinitiatedwitheithertheR/
Wsignalorthebyteenables.Failure
toobservethistimingcanresultinaglitchedinternalwriteinhibitsignaland
corrupted data in the slave.
Semaphores
The IDT70V35/34 (IDT70V25/24) is an extremely fast Dual-Port 8/
4K x 18 (8/4K x 16) CMOS Static RAM with an additional 8 address
locations dedicated to binary semaphore flags. These flags allow either
processorontheleftorrightsideoftheDual-PortSRAMtoclaimaprivilege
over the other processor for functions defined by the system designer’s
Functional Description
The IDT70V35/34 (IDT70V25/24) provides two ports with separate
control, address and I/O pins that permit independent access for reads or
writes to any location in memory. The IDT70V35/34 (IDT70V25/24) has
an automatic power down feature controlled by
CE. TheCEcontrolson-
chip power down circuitry that permits the respective port to go into a
standby mode when not selected (
CE HIGH). When a port is enabled,
access to the entire memory array is permitted.
Interrupts
Iftheuserchoosestheinterruptfunction,amemorylocation(mailbox
or message center) is assigned to each port. The left port interrupt flag
(
INTL) is asserted when the right port writes to memory location 1FFE
(HEX) (FFE for IDT70V34 and IDT70V24), where a write is defined as
the
CER=R/WR=VIL perTruthTableIII.Theleftportclearstheinterrupt
on the IDT70V35 and IDT70V25 by an address location 1FFE (FFE for
IDT70V34andIDT70V24)accesswhen
CEL=OEL=VIL,R/WLisa"don't
care". Likewise, the right port interrupt flag (
INTR)issetwhentheleftport
writestomemorylocation1FFFforIDT70V35andIDT70V25(HEX)(FFF
for IDT70V34 and IDT70V24) and to clear the interrupt flag (
INTR), the
right port must read the memory location 1FFF for IDT70V35 and
IDT70V25 (FFF for IDT70V34 and IDT70V24). The message (16 bits)
at 1FFE or 1FFF for IDT70V35 and IDT70V25 (FFE or FFF for
IDT70V34 and IDT70V24) is user-defined, since it is an addressable
SRAMlocation.Iftheinterruptfunctionisnotused,addresslocations1FFE
and 1FFF for IDT70V35 and IDT70V25 (FFE and FFF for IDT70V34 and
IDT70V24) are not used as mail boxes, but as part of the random access
memory. Refer to Truth Table III for the interrupt operation.
Busy Logic
BusyLogicprovidesahardwareindicationthatbothportsoftheSRAM
haveaccessedthesamelocationatthesametime.Italsoallowsoneofthe
twoaccessestoproceedandsignalstheothersidethattheSRAMis“busy”.
The
BUSYpincanthenbeusedtostalltheaccessuntiltheoperationon
the other side is completed. If a write operation has been attempted from
thesidethatreceivesa
BUSYindication,thewritesignalisgatedinternally
to prevent the write from proceeding.
The use of
BUSYlogicisnotrequiredordesirableforallapplications.
In some cases it may be useful to logically OR the
BUSYoutputstogether
and use any
BUSY indication as an interrupt source to flag the event of
an illegal or illogical operation. If the write inhibit function of
BUSYlogicis
5624 drw 19
MASTER
Dual Port
SRAM
BUSYL
BUSYR
CE
MASTER
Dual Port
SRAM
BUSYL
BUSYR
CE
SLAVE
Dual Port
SRAM
BUSYL
BUSYR
CE
SLAVE
Dual Port
SRAM
BUSYL
BUSYR
CE
BUSYL
BUSYR
D
E
C
O
D
E
R
,
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