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参数资料
| 型号： | IDT7026L20G |
| 厂商： | IDT, Integrated Device Technology Inc |
| 文件页数： | 17/18页 |
| 文件大小： | 0K |
| 描述： | IC SRAM 256KBIT 20NS 84PGA |
| 标准包装： | 3 |
| 格式 - 存储器： | RAM |
| 存储器类型： | SRAM - 双端口，异步 |
| 存储容量： | 256K（16K x 16） |
| 速度： | 20ns |
| 接口： | 并联 |
| 电源电压： | 4.5 V ~ 5.5 V |
| 工作温度： | 0°C ~ 70°C |
| 封装/外壳： | 84-BPGA |
| 供应商设备封装： | 84-PGA（27.94x27.94） |
| 包装： | 托盘 |
| 其它名称： | 7026L20G |
IDT7026S/L
High-Speed 16K x 16 Dual-Port Static RAM
Military, Industrial and Commercial Temperature Ranges
L PORT
SEMAPHORE
REQUEST FLIP FLOP
D 0 D Q
WRITE
R PORT
SEMAPHORE
REQUEST FLIP FLOP
Q D D 0
WRITE
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
SEMAPHORE
READ
SEMAPHORE
READ
2939 drw 17
Figure 4. IDT7026 Semaphore Logic
,
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-
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 Dual-Port RAM,
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 8K. 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
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 processors can access their assigned RAM
segments at full speed.
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 guaranteeing a consistent data structure.
point, the software could choose to try and gain control of the second 8K
17
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| IDT7026L20J | 功能描述:IC SRAM 256KBIT 20NS 84PLCC RoHS:否 类别:集成电路 (IC) >> 存储器 系列:- 标准包装:1,000 系列:- 格式 - 存储器:RAM 存储器类型:SRAM - 双端口，同步 存储容量:1.125M（32K x 36） 速度:5ns 接口:并联 电源电压:3.15 V ~ 3.45 V 工作温度:-40°C ~ 85°C 封装/外壳:256-LBGA 供应商设备封装:256-CABGA（17x17） 包装:带卷 (TR) 其它名称:70V3579S5BCI8 |
| IDT7026L20J8 | 功能描述:IC SRAM 256KBIT 20NS 84PLCC RoHS:否 类别:集成电路 (IC) >> 存储器 系列:- 标准包装:1,000 系列:- 格式 - 存储器:RAM 存储器类型:SRAM - 双端口，同步 存储容量:1.125M（32K x 36） 速度:5ns 接口:并联 电源电压:3.15 V ~ 3.45 V 工作温度:-40°C ~ 85°C 封装/外壳:256-LBGA 供应商设备封装:256-CABGA（17x17） 包装:带卷 (TR) 其它名称:70V3579S5BCI8 |
| IDT7026L20JI | 功能描述:IC SRAM 256KBIT 20NS 84PLCC RoHS:否 类别:集成电路 (IC) >> 存储器 系列:- 标准包装:1,000 系列:- 格式 - 存储器:RAM 存储器类型:SRAM - 双端口，同步 存储容量:1.125M（32K x 36） 速度:5ns 接口:并联 电源电压:3.15 V ~ 3.45 V 工作温度:-40°C ~ 85°C 封装/外壳:256-LBGA 供应商设备封装:256-CABGA（17x17） 包装:带卷 (TR) 其它名称:70V3579S5BCI8 |
| IDT7026L20JI8 | 功能描述:IC SRAM 256KBIT 20NS 84PLCC RoHS:否 类别:集成电路 (IC) >> 存储器 系列:- 标准包装:1,000 系列:- 格式 - 存储器:RAM 存储器类型:SRAM - 双端口，同步 存储容量:1.125M（32K x 36） 速度:5ns 接口:并联 电源电压:3.15 V ~ 3.45 V 工作温度:-40°C ~ 85°C 封装/外壳:256-LBGA 供应商设备封装:256-CABGA（17x17） 包装:带卷 (TR) 其它名称:70V3579S5BCI8 |
| IDT7026L25G | 功能描述:IC SRAM 256KBIT 25NS 84PGA RoHS:否 类别:集成电路 (IC) >> 存储器 系列:- 标准包装:3,000 系列:- 格式 - 存储器:EEPROMs - 串行 存储器类型:EEPROM 存储容量:8K (1K x 8) 速度:400kHz 接口:I²C，2 线串口 电源电压:1.7 V ~ 5.5 V 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 供应商设备封装:8-SOIC 包装:带卷 (TR) |
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