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參數(shù)資料
| 型號(hào)： | IDT70V25S55PF |
| 廠商： | INTEGRATED DEVICE TECHNOLOGY INC |
| 元件分類： | DRAM |
| 英文描述： | HIGH-SPEED 3.3V 8K x 16 DUAL-PORT STATIC RAM |
| 中文描述： | 8K X 16 DUAL-PORT SRAM, 55 ns, PQFP100 |
| 封裝： | 14 X 14 MM, 1.40 MM HEIGHT, PLASTIC, TQFP-100 |
| 文件頁(yè)數(shù)： | 14/17頁(yè) |
| 文件大?。?/td> | 276K |
| 代理商： | IDT70V25S55PF |
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IDT70V25S/L
HIGH-SPEED 3.3V 8K x 16 DUAL-PORT STATIC RAM
COMMERCIAL TEMPERATURE RANGE
Figure 3. Busy and chip enable routing for both width and depth expansion with IDT70V25 RAMs.
inhibit signal and corrupted data in the slave.
SEMAPHORES
The IDT70V25 is an extremely fast Dual-Port 8K x 16
CMOS Static RAM with an additional 8 address locations
dedicated to binary semaphore flags. These flags allow either
processor on the left or right side of the Dual-Port RAM to claim
a privilege over the other processor for functions defined by
the system designer’s software. As an example, the sema-
phore can be used by one processor to inhibit the other from
accessing a portion of the Dual-Port RAM or any other shared
resource.
The Dual-Port RAM features a fast access time, and both
ports are completely independent of each other. This means
that the activity on the left port in no way slows the access time
of the right port. Both ports are identical in function to standard
CMOS Static RAM and can be read from, or written to, at the
same time with the only possible conflict arising from the
simultaneous writing of, or a simultaneous READ/WRITE of,
a non-semaphore location. Semaphores are protected against
such ambiguous situations and may be used by the system
program to avoid any conflicts in the non-semaphore portion
of the Dual-Port RAM. These devices have an automatic
power-down feature controlled by
CE
, the Dual-Port RAM
enable, and
SEM
, the semaphore enable. The
CE
and
SEM
pins control on-chip power down circuitry that permits the
respective port to go into standby mode when not selected.
This is the condition which is shown in Truth Table where
CE
and
SEM
are both high.
Systems which can best use the IDT70V25 contain mul-
tiple processors or controllers and are typically very high-
speed systems which are software controlled or software
intensive. These systems can benefit from a performance
increase offered by the IDT70V25's hardware semaphores,
which provide a lockout mechanism without requiring com-
plex programming.
Software handshaking between processors offers the maxi-
mum in system flexibility by permitting shared resources to be
allocated in varying configurations. The IDT70V25 does not
use its semaphore flags to control any resources through
2944 drw 18
MASTER
Dual Port
RAM
BUSY
L
BUSY
R
CE
MASTER
Dual Port
RAM
BUSY
L
BUSY
R
CE
SLAVE
Dual Port
RAM
BUSY
L
BUSY
R
CE
SLAVE
Dual Port
RAM
BUSY
L
BUSY
R
CE
BUSY
L
BUSY
R
D
applications. In some cases it may be useful to logically OR
the busy outputs together 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 busy logic is not
desirable, the busy logic can be disabled by placing the part
in slave mode with the M/
S
pin. Once in slave mode the
BUSY
pin operates solely as a write inhibit input pin. Normal opera-
tion 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 IDT 70V25 RAM in master mode,
are push-pull type outputs and do not require pull up resistors
to operate. If these RAMs are being expanded in depth, then
the busy indication for the resulting array requires the use of
an external AND gate.
WIDTH EXPANSION WITH BUSY LOGIC
MASTER/SLAVE ARRAYS
When expanding an IDT70V25 RAM array in width while
using busy logic, one master part is used to decide which side
of the RAM 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 IDT70V25 RAM the busy pin
is an output if the part is used as a master (M/
S
pin = H), and
the busy pin is an input if the part used as a slave (M/
S
pin =
L) as shown in Figure 3.
If two or more master parts were used when expanding in
width, a split decision could result with one master indicating
busy on one side of the array and another master indicating
busy on one other side of the array. This would inhibit the write
operations from one port for part of a word and inhibit the write
operations from the other port for the other part of the word.
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 enough for a busy flag to be
output from the master before the actual write pulse can be
initiated with either the R/
W
signal or the byte enables. Failure
to observe this timing can result in a glitched internal write
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| IDT70V25S55PF8 | 功能描述:IC SRAM 128KBIT 55NS 100TQFP RoHS:否 類別:集成電路 (IC) >> 存儲(chǔ)器 系列:- 標(biāo)準(zhǔn)包裝:72 系列:- 格式 - 存儲(chǔ)器:RAM 存儲(chǔ)器類型:SRAM - 同步 存儲(chǔ)容量:9M（256K x 36） 速度:75ns 接口:并聯(lián) 電源電壓:3.135 V ~ 3.465 V 工作溫度:-40°C ~ 85°C 封裝/外殼:100-LQFP 供應(yīng)商設(shè)備封裝:100-TQFP（14x14） 包裝:托盤 其它名稱:71V67703S75PFGI |
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