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| 型号： | IDT70T659S10BC |
| 厂商： | IDT, Integrated Device Technology Inc |
| 文件页数： | 23/27页 |
| 文件大小： | 0K |
| 描述： | IC SRAM 4MBIT 10NS 256BGA |
| 标准包装： | 6 |
| 格式 - 存储器： | RAM |
| 存储器类型： | SRAM - 双端口，异步 |
| 存储容量： | 4.5M（128K x 36） |
| 速度： | 10ns |
| 接口： | 并联 |
| 电源电压： | 2.4 V ~ 2.6 V |
| 工作温度： | 0°C ~ 70°C |
| 封装/外壳： | 256-LBGA |
| 供应商设备封装： | 256-CABGA（17x17） |
| 包装： | 托盘 |
| 其它名称： | 70T659S10BC |
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IDT70T651/9S
High-Speed 2.5V 256/128K x 36 Asynchronous Dual-Port Static RAM
Industrial and Commercial Temperature Ranges
verifies its success in setting the latch by reading it. If it was successful, it
proceeds to assume control over the shared resource. If it was not
successful in setting the latch, it determines that the right side processor
has set the latch first, has the token and is using the shared resource.
The left processor can then either repeatedly request that
semaphore’s status or remove its request for that semaphore to
perform another task and occasionally attempt again to gain control of
the token via the set and test sequence. Once the right side has
relinquished the token, the left side should succeed in gaining control.
The semaphore flags are active LOW. A token is requested by
writing a zero into a semaphore latch and is released when the same
side writes a one to that latch.
The eight semaphore flags reside within the IDT70T651/9 in a
separate memory space from the Dual-Port RAM. This address space
is accessed by placing a low input on the SEM pin (which acts as a chip
the gap between the read and write cycles.
It is important to note that a failed semaphore request must be followed
by either repeated reads or by writing a one into the same location. The
reason for this is easily understood by looking at the
simple logic diagram of the semaphore flag in Figure 4. Two semaphore
request latches feed into a semaphore flag. Whichever latch is first to
present a zero to the semaphore flag will force its side of the semaphore
flag LOW and the other side HIGH. This condition will continue until a one
is written to the same semaphore request latch. If the opposite side
semaphore request latch has been written to zero in the meantime, the
semaphore flag will flip over to the other side as soon as a one is written
into the first request latch. The opposite side flag will now stay LOW until
its semaphore request latch is written to a one. From this it is easy to
select for the semaphore flags) and using the other control pins (Address,
CE 0 , CE 1 ,R/ W and BE n) as they would be used in accessing a
standard Static RAM. Each of the flags has a unique address which can
L PORT
SEMAPHORE
REQUEST FLIP FLOP
R PORT
SEMAPHORE
REQUEST FLIP FLOP
be accessed by either side through address pins A 0 – A 2 . When accessing
the semaphores, none of the other address pins has any effect.
D 0
D
Q
Q
D
D 0
When writing to a semaphore, only data pin D 0 is used. If a low level
is written into an unused semaphore location, that flag will be set to
a zero on that side and a one on the other side (see Truth Table V).
That semaphore can now only be modified by the side showing the zero.
When a one is written into the same location from the same side, the flag
will be set to a one for both sides (unless a semaphore request
WRITE
SEMAPHORE
READ
Figure 4. IDT70T651/9 Semaphore Logic
WRITE
SEMAPHORE
READ
5632 drw 21
from the other side is pending) and then can be written to by both sides.
The fact that the side which is able to write a zero into a semaphore
subsequently locks out writes from the other side is what makes
semaphore flags useful in interprocessor communications. (A thorough
discussion on the use of this feature follows shortly.) A zero written into the
same location from the other side will be stored in the semaphore request
latch for that side until the semaphore is freed by the first side.
When a semaphore flag is read, its value is spread into all data bits so
that a flag that is a one reads as a one in all data bits and a flag containing
a zero reads as all zeros for a semaphore read, the SEM , BE n, and OE
signals need to be active. (Please refer to Truth Table II). Furthermore,
the read value is latched into one side’s output register when that side's
semaphore select ( SEM , BE n) and output enable ( OE ) signals go active.
This serves to disallow the semaphore from changing state in the middle
of a read cycle due to a write cycle from the other side.
A sequence WRITE/READ must be used by the semaphore in
order to guarantee that no system level contention will occur. A
processor requests access to shared resources by attempting to write
a zero into a semaphore location. If the semaphore is already in use,
the semaphore request latch will contain a zero, yet the semaphore
flag will appear as one, a fact which the processor will verify by the
subsequent read (see Table V). As an example, assume a processor
writes a zero to the left port at a free semaphore location. On a
subsequent read, the processor will verify that it has written success-
fully to that location and will assume control over the resource in
question. Meanwhile, if a processor on the right side attempts to write
a zero to the same semaphore flag it will fail, as will be verified by the
fact that a one will be read from that semaphore on the right side
during subsequent read. Had a sequence of READ/WRITE been
used instead, system contention problems could have occurred during
23
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 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.
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相关代理商/技术参数 |
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| IDT70T659S10BC8 | 功能描述:IC SRAM 4MBIT 10NS 256BGA 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) |
| IDT70T659S10BCI | 功能描述:IC SRAM 4MBIT 10NS 256BGA 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) |
| IDT70T659S10BCI8 | 功能描述:IC SRAM 4MBIT 10NS 256BGA 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) |
| IDT70T659S10BF | 功能描述:IC SRAM 4MBIT 10NS 208FBGA 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) |
| IDT70T659S10BF8 | 功能描述:IC SRAM 4MBIT 10NS 208FBGA 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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