7025L20JGI IDT, 7025L20JGI Datasheet - Page 21

• Manufacturer Part Number: 7025L20JGI
• Description: SRAM
• Manufacturer: IDT
• Series: IDT7025S/Lr
• Type: Dual Port RAMr

Specifications of 7025L20JGI

• Rohs: yes
• Memory Size: 128 Kbit
• Organization: 8 K x 16
• Access Time: 20 ns
• Supply Voltage - Max: 5.5 V
• Supply Voltage - Min: 4.5 V
• Maximum Operating Current: 320 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Package / Case: PLCC-84
• Interface: TTL
• Memory Type: Asynchronous
• Part # Aliases: IDT7025L20JGI

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.
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.
state is available on one or both sides. Once a semaphore handshake has
IDT7025S/L
High-Speed 8K x 16 Dual-Port Static RAM
Semaphores are a useful form of arbitration in systems like disk
Semaphores are also useful in applications where no memory “WAIT”
SEMAPHORE
WRITE
L PORT
D
REQUEST FLIP FLOP
0
READ
SEMAPHORE
D
Figure 4. IDT7025 Semaphore Logic
Q
6.42
21
been performed, both processors can access their assigned RAM
segments at full speed.
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.
Another application is in the area of complex data structures. In this
REQUEST FLIP FLOP
SEMAPHORE
Military, Industrial and Commercial Temperature Ranges
Q
D
SEMAPHORE
READ
R PORT
D
WRITE
2683 drw 20
0
.