IDT70T3589 Integrated Device Technology, IDT70T3589 Datasheet - Page 23

• Manufacturer Part Number: IDT70T3589
• Description: 64k X 36 Sync, 3.3v/2.5v Dual-port Ram, Interleaved I/o S
• Manufacturer: Integrated Device Technology

Functional Description
RAM interface. Registered inputs provide minimal set-up and hold times
on address, data, and all critical control inputs. All internal registers are
clocked on the rising edge of the clock signal, however, the self-timed
internal write pulse width is independent of the cycle time.
chronous bus interfacing. Counter enable inputs are also provided to stall
the operation of the address counters for fast interleaved
memory applications.
the internal circuitry to reduce static power consumption. Multiple chip
enables allow easier banking of multiple IDT70T3519/99/89s for depth
expansion configurations. Two cycles are required with CE
CE
Interrupts
flag (INT
3FFFE (HEX), where a write is defined as CE
Truth Table. The left port clears the interrupt through access of
address location 3FFFE when CE
right port interrupt flag (INT
port writes to memory location 3FFFF (HEX) and to clear the interrupt
flag (INT
or 1FFFE for IDT70T3599 and FFFF or FFFE for IDT70T3589). The
message (36 bits) at 3FFFE or 3FFFF (1FFFF or 1FFFE for IDT70T3599
and FFFF or FFFE for IDT70T3589) is user-defined since it is an
addressable SRAM location. If the interrupt function is not used, address
locations 3FFFE and 3FFFF (1FFFF or 1FFFE for IDT70T3599 and
FFFF or FFFE for IDT70T3589) are not used as mail boxes, but as part
of the random access memory. Refer to Truth Table III for the interrupt
operation.
Collision Detection
resulting in the potential for either reading or writing incorrect data to a
specific address. For the specific cases: (a) Both ports reading - no
data is corrupted, lost, or incorrectly output, so no collision flag is output
on either port. (b) One port writing, the other port reading - the end
result of the write will still be valid. However, the reading port might
capture data that is in a state of transition and hence the reading port’s
collision flag is output. (c) Both ports writing - there is a risk that the two
ports will interfere with each other, and the data stored in memory will
not be a valid write from either port (it may essentially be a random
combination of the two). Therefore, the collision flag is output on both
ports. Please refer to Truth Table IV for all of the above cases.
edge of the affected port following the collision, and remains low for
one cycle. Please refer to Collision Detection Timing table on Page 21.
During that next cycle, the internal arbitration is engaged in resetting
the alert flag (this avoids a specific requirement on the part of the user
to reset the alert flag). If two collisions occur on subsequent clock
cycles, the second collision may not generate the appropriate alert
box or message center) is assigned to each port. The left port interrupt
IDT70T3519/99/89S
High-Speed 2.5V 256/128/64K x 36 Dual-Port Synchronous Static RAM
The IDT70T3519/99/89 provides a true synchronous Dual-Port Static
An asynchronous output enable is provided to ease asyn-
1
Collision is defined as an overlap in access between the two ports
A HIGH on CE
If the user chooses the interrupt function, a memory location (mail
The alert flag (COL
HIGH to re-activate the outputs.
R
L
), the right port must read the memory location 3FFFF (1FFFF
) is asserted when the right port writes to memory location
0
or a LOW on CE
X
) is asserted on the 2nd or 3rd rising clock
L
1
= V
R
for one clock cycle will power down
) is asserted when the left
IL
and R/WL = V
R
= R/W
IH
R
. Likewise, the
= V
0
LOW and
IL
per the
6.42
23
significant advance in functionality over current sync multi-ports, which
have no such capability. In addition to this functionality the
IDT70T3519/99/89 sustains the key features of bandwidth and
flexibility. The collision detection function is very useful in the case of
bursting data, or a string of accesses made to sequential addresses, in
that it indicates a problem within the burst, giving the user the option of
either repeating the burst or continuing to watch the alert flag to see
whether the number of collisions increases above an acceptable
threshold value. Offering this function on chip also allows users to
reduce their need for arbitration circuits, typically done in CPLD’s or
FPGA’s. This reduces board space and design complexity, and gives
the user more flexibility in developing a solution.
Sleep Mode
flag. A third collision will generate the alert flag as appropriate. In the
event that a user initiates a burst access on both ports with the same
starting address on both ports and one or both ports writing during
each access (i.e., imposes a long string of collisions on contiguous
clock cycles), the alert flag will be asserted and cleared every other
cycle. Please refer to the Collision Detection timing waveform on Page
21.
power mode on both ports. The sleep mode pin on both ports is
asynchronous and active high. During normal operation, the ZZ pin is
pulled low. When ZZ is pulled high, the port will enter sleep mode where
it will meet lowest possible power conditions. The sleep mode timing
diagram shows the modes of operation: Normal Operation, No Read/Write
Allowed and Sleep Mode.
to sleep and after recovering from sleep. Clocks must also meet cycle high
and low times during these periods. Three cycles prior to asserting ZZ
(ZZx = V
must be disabled via the chip enable pins. If a write or read operation occurs
during these periods, the memory array may be corrupted. Validity of data
out from the RAM cannot be guaranteed immediately after ZZ is asserted
(prior to being in sleep). When exiting sleep mode, the device must be in
Read mode (R/Wx = V
enable must be valid for one full cycle before a read will result in the output
of valid data.
disconnects its internal clock buffer. The external clock may continue to run
without impacting the RAMs sleep current (I
high-Z state while in sleep mode. All inputs are allowed to toggle. The RAM
will not be selected and will not perform any reads or writes.
Collision detection on the IDT70T3519/99/89 represents a
The IDT70T3519/99/89 is equipped with an optional sleep or low
For normal operation all inputs must meet setup and hold times prior
During sleep mode the RAM automatically deselects itself. The RAM
IH
) and three cycles after de-asserting ZZ (ZZx = V
Industrial and Commercial Temperature Ranges
IH
)when chip enable is asserted, and the chip
ZZ
). All outputs will remain in
APRIL 10, 2006
IL
), the device