- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄377269 > IDT7026L20GB (INTEGRATED DEVICE TECHNOLOGY INC) HIGH-SPEED 16K x 16 DUAL-PORT STATIC RAM PDF資料下載
參數(shù)資料
| 型號： | IDT7026L20GB |
| 廠商： | INTEGRATED DEVICE TECHNOLOGY INC |
| 元件分類： | DRAM |
| 英文描述： | HIGH-SPEED 16K x 16 DUAL-PORT STATIC RAM |
| 中文描述： | 16K X 16 DUAL-PORT SRAM, 20 ns, CPGA84 |
| 封裝： | CERAMIC, PGA-84 |
| 文件頁數(shù)： | 17/18頁 |
| 文件大小： | 239K |
| 代理商： | IDT7026L20GB |
IDT7026S/L
HIGH-SPEED 16K x 16 DUAL-PORT STATIC RAM
MILITARY AND COMMERCIAL TEMPERATURE RANGES
6.17
17
D
2939 drw 17
0
D
Q
WRITE
D
0
WRITE
D
Q
SEMAPHORE
REQUEST FLIP FLOP
SEMAPHORE
REQUEST FLIP FLOP
L PORT
R PORT
SEMAPHORE
READ
SEMAPHORE
READ
Dual-Port RAM, the processor on the left port could write and
then read a zero in to Semaphore 0. If this task were success-
fully completed (a zero was read back rather than a one), the
left processor would assume control of the lower 8K. Mean-
while 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 and gain
control of the second 8K section by writing, then reading a zero
into Semaphore 1. If it succeeded in gaining control, it would
lock out the left side.
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 Semaphore 1 was still occupied by the right
side, the left side could undo its semaphore request and
perform other tasks until it was able to write, then read a zero
into Semaphore 1. If the right processor performs a similar
task with Semaphore 0, this protocol would allow the two
processors to swap 8K blocks of Dual-Port RAM 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-Port RAM or other shared
resources into eight parts. 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 continuously 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 proces-
sors can access their assigned RAM segments at full speed.
Another application is in the area of complex data struc-
tures. 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 guaranteeing a consistent data structure.
one is written to the same semaphore request latch. Should
the other side’s semaphore request latch have been written to
a zero in the meantime, the semaphore flag will flip over to the
other side as soon as a one is written into the first side’s
request latch. The second side’s flag will now stay LOW until
its semaphore request latch is written to a one. From this it is
easy to understand that, if a semaphore is requested and the
processor which requested it no longer needs the resource,
the entire system can hang up until a one is written into that
semaphore request latch.
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 semaphore 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.
USING SEMAPHORES—SOME EXAMPLES
Perhaps the simplest application of semaphores is their
application as resource markers for the IDT7026’s Dual-Port
RAM. Say the 16K x 16 RAM was to be divided into two 8K
x 16 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 8K of
Figure 4. IDT7026 Semaphore Logic
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| IDT7026L20J | HIGH-SPEED 16K x 16 DUAL-PORT STATIC RAM |
| IDT7026L20JB | HIGH-SPEED 16K x 16 DUAL-PORT STATIC RAM |
| IDT7026L25G | HIGH-SPEED 16K x 16 DUAL-PORT STATIC RAM |
| IDT7026L25GB | HIGH-SPEED 16K x 16 DUAL-PORT STATIC RAM |
| IDT7026L25J | HIGH-SPEED 16K x 16 DUAL-PORT STATIC RAM |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| IDT7026L20J | 功能描述:IC SRAM 256KBIT 20NS 84PLCC RoHS:否 類別:集成電路 (IC) >> 存儲器 系列:- 標準包裝:1,000 系列:- 格式 - 存儲器:RAM 存儲器類型:SRAM - 雙端口，同步 存儲容量:1.125M（32K x 36） 速度:5ns 接口:并聯(lián) 電源電壓:3.15 V ~ 3.45 V 工作溫度:-40°C ~ 85°C 封裝/外殼:256-LBGA 供應(yīng)商設(shè)備封裝:256-CABGA（17x17） 包裝:帶卷 (TR) 其它名稱:70V3579S5BCI8 |
| IDT7026L20J8 | 功能描述:IC SRAM 256KBIT 20NS 84PLCC RoHS:否 類別:集成電路 (IC) >> 存儲器 系列:- 標準包裝:1,000 系列:- 格式 - 存儲器:RAM 存儲器類型:SRAM - 雙端口，同步 存儲容量:1.125M（32K x 36） 速度:5ns 接口:并聯(lián) 電源電壓:3.15 V ~ 3.45 V 工作溫度:-40°C ~ 85°C 封裝/外殼:256-LBGA 供應(yīng)商設(shè)備封裝:256-CABGA（17x17） 包裝:帶卷 (TR) 其它名稱:70V3579S5BCI8 |
| IDT7026L20JI | 功能描述:IC SRAM 256KBIT 20NS 84PLCC RoHS:否 類別:集成電路 (IC) >> 存儲器 系列:- 標準包裝:1,000 系列:- 格式 - 存儲器:RAM 存儲器類型:SRAM - 雙端口，同步 存儲容量:1.125M（32K x 36） 速度:5ns 接口:并聯(lián) 電源電壓:3.15 V ~ 3.45 V 工作溫度:-40°C ~ 85°C 封裝/外殼:256-LBGA 供應(yīng)商設(shè)備封裝:256-CABGA（17x17） 包裝:帶卷 (TR) 其它名稱:70V3579S5BCI8 |
| IDT7026L20JI8 | 功能描述:IC SRAM 256KBIT 20NS 84PLCC RoHS:否 類別:集成電路 (IC) >> 存儲器 系列:- 標準包裝:1,000 系列:- 格式 - 存儲器:RAM 存儲器類型:SRAM - 雙端口，同步 存儲容量:1.125M（32K x 36） 速度:5ns 接口:并聯(lián) 電源電壓:3.15 V ~ 3.45 V 工作溫度:-40°C ~ 85°C 封裝/外殼:256-LBGA 供應(yīng)商設(shè)備封裝:256-CABGA（17x17） 包裝:帶卷 (TR) 其它名稱:70V3579S5BCI8 |
| IDT7026L25G | 功能描述:IC SRAM 256KBIT 25NS 84PGA RoHS:否 類別:集成電路 (IC) >> 存儲器 系列:- 標準包裝:3,000 系列:- 格式 - 存儲器:EEPROMs - 串行 存儲器類型:EEPROM 存儲容量:8K (1K x 8) 速度:400kHz 接口:I²C，2 線串口 電源電壓:1.7 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:8-SOIC 包裝:帶卷 (TR) |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。