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參數(shù)資料
| 型號： | 70V05L35PF8 |
| 廠商： | INTEGRATED DEVICE TECHNOLOGY INC |
| 元件分類： | SRAM |
| 英文描述： | 8K X 8 DUAL-PORT SRAM, 35 ns, PQFP64 |
| 封裝： | 14 X 14 MM, 1.40 MM HEIGHT, TQFP-64 |
| 文件頁數(shù)： | 14/22頁 |
| 文件大小： | 159K |
| 代理商： | 70V05L35PF8 |
6.42
IDT70V05S/L
High-Speed 3.3V 8K x 8 Dual-Port Static RAM
Industrial and Commercial Temperature Ranges
21
D0
2941 drw 19
D
Q
WRITE
D0
D
Q
WRITE
SEMAPHORE
REQUEST FLIP FLOP
SEMAPHORE
REQUEST FLIP FLOP
L PORT
R PORT
SEMAPHORE
READ
SEMAPHORE
READ
The critical case of semaphore timing is when both sides request a
single token by attempting to write a zero into it at the same time. The
semaphore logic is specially designed to resolve this problem. If
simultaneous requests are made, the logic guarantees that only one
side receives the token. If one side is earlier than the other in making
the request, the first side to make the request will receive the token. If
both requests arrive at the same time, the assignment will be arbitrarily
made to one port or the other.
One caution that should be noted when using semaphores is that
semaphores alone do not guarantee that access to a resource is
secure. As with any powerful programming technique, if semaphores
are misused or misinterpreted, a software error can easily happen.
Initialization of the semaphores is not automatic and must be
handled via the initialization program at power-up. Since any sema-
phore request flag which contains a zero must be reset to a one, all
semaphores on both sides should have a one written into them at
initialization from both sides to assure that they will be free when
needed.
UsingSemaphores—SomeExamples
Perhaps the simplest application of semaphores is their applica-
tion as resource markers for the IDT70V05’s Dual-Port SRAM. Say the
8K x 8 SRAM was to be divided into two 4K x 8 blocks which were to be
dedicated at any one time to servicing either the left or right port.
Semaphore 0 could be used to indicate the side which would control
the lower section of memory, and Semaphore 1 could be defined as the
indicator for the upper section of memory.
To take a resource, in this example the lower 4K of Dual-Port
SRAM, the processor on the left port could write and then read a
zero in to Semaphore 0. If this task were successfully completed
(a zero was read back rather than a one), the left processor would
assume control of the lower 4K. Meanwhile the right processor was
attempting to gain control of the resource after the left processor, it
would read back a one in response to the zero it had attempted to
write into Semaphore 0. At this point, the software could choose to try
andgaincontrolofthesecond4Ksectionbywriting,thenreadingazero
into Semaphore 1. If it succeeded in gaining control, it would lock out
theleftside.
Once the left side was finished with its task, it would write a one to
Semaphore 0 and may then try to gain access to Semaphore 1. If
Semaphore1wasstilloccupiedbytherightside,theleftsidecouldundo
itssemaphorerequestandperformothertasksuntilitwasabletowrite,then
readazerointoSemaphore1.Iftherightprocessorperformsasimilartask
withSemaphore0,thisprotocolwouldallowthetwoprocessorstoswap
4K blocks of Dual-Port SRAM with each other.
The blocks do not have to be any particular size and can even be
variable, depending upon the complexity of the software using the
semaphore flags. All eight semaphores could be used to divide the
Dual-PortSRAMorothersharedresourcesintoeightparts.Semaphores
can even be assigned different meanings on different sides rather than
being given a common meaning as was shown in the example above.
Semaphores are a useful form of arbitration in systems like disk
interfaces where the CPU must be locked out of a section of memory
during a transfer and the I/O device cannot tolerate any wait states.
With the use of semaphores, once the two devices has determined
which memory area was “off-limits” to the CPU, both the CPU and the
I/O devices could access their assigned portions of memory continu-
ously without any wait states.
Semaphores are also useful in applications where no memory
“WAIT” state is available on one or both sides. Once a semaphore
handshake has been performed, both processors can access their
assignedSRAMsegmentsatfullspeed.
Another application is in the area of complex data structures. In this
case, block arbitration is very important. For this application one
processor may be responsible for building and updating a data
structure. The other processor then reads and interprets that data
structure. If the interpreting processor reads an incomplete data
structure, a major error condition may exist. Therefore, some sort of
arbitration must be used between the two different processors. The
building processor arbitrates for the block, locks it and then is able to
go in and update the data structure. When the update is completed, the
data structure block is released. This allows the interpreting processor
to come back and read the complete data structure, thereby guaran-
teeing a consistent data structure.
Figure 4. IDT70V05 Semaphore Logic
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| 70V05L20J | 8K X 8 DUAL-PORT SRAM, 20 ns, PQCC68 |
| 70V05L35PF | 8K X 8 DUAL-PORT SRAM, 35 ns, PQFP64 |
| 70V05S15J8 | 8K X 8 DUAL-PORT SRAM, 15 ns, PQCC68 |
| 70V05S55G | 8K X 8 DUAL-PORT SRAM, 55 ns, CPGA68 |
| 70V05S55J8 | 8K X 8 DUAL-PORT SRAM, 55 ns, PQCC68 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 70V05L35PFI | 制造商:Integrated Device Technology Inc 功能描述:SRAM ASYNC DUAL 3.3V 64KBIT 8KX8 35NS 64TQFP - Bulk |
| 70V05L35PFI8 | 功能描述:IC SRAM 64KBIT 64TQFP 制造商:idt, integrated device technology inc 系列:* 零件狀態(tài):最後搶購 標準包裝:750 |
| 70V05L55G | 制造商:Integrated Device Technology Inc 功能描述:SRAM ASYNC DUAL 3.3V 64KBIT 8KX8 55NS 68PIN PGA - Trays |
| 70V05L55J | 功能描述:靜態(tài)隨機存取存儲器 8K x 8 3.3v Dual- Port Ram RoHS:否 制造商:Cypress Semiconductor 存儲容量:16 Mbit 組織:1 M x 16 訪問時間:55 ns 電源電壓-最大:3.6 V 電源電壓-最小:2.2 V 最大工作電流:22 uA 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSOP-48 封裝:Tray |
| 70V05L55J8 | 功能描述:靜態(tài)隨機存取存儲器 8K x 8 3.3v Dual- Port Ram RoHS:否 制造商:Cypress Semiconductor 存儲容量:16 Mbit 組織:1 M x 16 訪問時間:55 ns 電源電壓-最大:3.6 V 電源電壓-最小:2.2 V 最大工作電流:22 uA 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSOP-48 封裝:Tray |
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