CY7C037-15AC Cypress Semiconductor Corp, CY7C037-15AC Datasheet - Page 15
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CY7C037-15AC
Manufacturer Part Number
CY7C037-15AC
Description
IC SRAM 576KBIT 15NS 100LQFP
Manufacturer
Cypress Semiconductor Corp
Datasheet
1.CY7C037-15AC.pdf
(19 pages)
Specifications of CY7C037-15AC
Format - Memory
RAM
Memory Type
SRAM - Dual Port, Asynchronous
Memory Size
576K (32K x 18)
Speed
15ns
Interface
Parallel
Voltage - Supply
4.5 V ~ 5.5 V
Operating Temperature
0°C ~ 70°C
Package / Case
100-LQFP
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Other names
428-1168
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
CY7C037-15AC
Manufacturer:
CY
Quantity:
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Company:
Part Number:
CY7C037-15AC
Manufacturer:
CYPRESS
Quantity:
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Company:
Part Number:
CY7C037-15AC
Manufacturer:
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Quantity:
10 000
Architecture
The CY7C027/028 and CY7C037/038 consist of an array of
32K and 64K words of 16 and 18 bits each of dual-port RAM
cells, I/O and address lines, and control signals (CE, OE, R/W).
These control pins permit independent access for reads or writes to
any location in memory. To handle simultaneous writes/reads to the
same location, a BUSY pin is provided on each port. Two interrupt
(INT) pins can be utilized for port-to-port communication. Two sema-
phore (SEM) control pins are used for allocating shared resources.
With the M/S pin, the devices can function as a master (BUSY pins
are outputs) or as a slave (BUSY pins are inputs). The devices also
have an automatic power-down feature controlled by CE. Each port
is provided with its own output enable control (OE), which allows data
to be read from the device.
Functional Description
Write Operation
Data must be set up for a duration of t
of R/W in order to guarantee a valid write. A write operation is con-
trolled by either the R/W pin (see Write Cycle No. 1 waveform) or the
CE pin (see Write Cycle No. 2 waveform). Required inputs for
non-contention operations are summarized in Table 1.
If a location is being written to by one port and the opposite
port attempts to read that location, a port-to-port flowthrough
delay must occur before the data is read on the output; other-
wise the data read is not deterministic. Data will be valid on the
port t
Read Operation
When reading the device, the user must assert both the OE
and CE pins. Data will be available t
asserted. If the user wishes to access a semaphore flag, then the
SEM pin must be asserted instead of the CE pin, and OE must also
be asserted.
Interrupts
The upper two memory locations may be used for message
passing. The highest memory location (7FFF for the
CY7C027/37, FFFF for the CY7C028/38) is the mailbox for the
right port and the second-highest memory location (7FFE for
the CY7C027/37, FFFE for the CY7C028/38) is the mailbox for
the left port. When one port writes to the other port’s mailbox,
an interrupt is generated to the owner. The interrupt is reset
when the owner reads the contents of the mailbox. The mes-
sage is user defined.
Each port can read the other port’s mailbox without resetting
the interrupt. The active state of the busy signal (to a port)
prevents the port from setting the interrupt to the winning port.
Also, an active busy to a port prevents that port from reading
its own mailbox and, thus, resetting the interrupt to it.
If an application does not require message passing, do not
connect the interrupt pin to the processor’s interrupt request
input pin.
The operation of the interrupts and their interaction with Busy
is summarized in Table 2.
Busy
The CY7C027/028 and CY7C037/038 provide on-chip arbitra-
tion to resolve simultaneous memory location access (conten-
Document #: 38-06042 Rev. *A
DDD
after the data is presented on the other port.
ACE
after CE or t
SD
before the rising edge
DOE
after OE is
tion). If both ports’ CEs are asserted and an address match occurs
within t
access. If t
location, but it is not predictable which port will get that permission.
BUSY will be asserted t
is taken LOW.
Master/Slave
A M/S pin is provided in order to expand the word width by configur-
ing the device as either a master or a slave. The BUSY output of the
master is connected to the BUSY input of the slave. This will allow the
device to interface to a master device with no external components.
Writing to slave devices must be delayed until after the BUSY input
has settled (t
cycle during a contention situation. When tied HIGH, the M/S pin al-
lows the device to be used as a master and, therefore, the BUSY line
is an output. BUSY can then be used to send the arbitration outcome
to a slave.
Semaphore Operation
The CY7C027/028 and CY7C037/038 provide eight sema-
phore latches, which are separate from the dual-port memory
locations. Semaphores are used to reserve resources that are
shared between the two ports.The state of the semaphore in-
dicates that a resource is in use. For example, if the left port
wants to request a given resource, it sets a latch by writing a
zero to a semaphore location. The left port then verifies its
success in setting the latch by reading it. After writing to the
semaphore, SEM or OE must be deasserted for t
tempting to read the semaphore. The semaphore value will be avail-
able t
left port was successful (reads a zero), it assumes control of the
shared resource, otherwise (reads a one) it assumes the right port
has control and continues to poll the semaphore. When the right side
has relinquished control of the semaphore (by writing a one), the left
side will succeed in gaining control of the semaphore. If the left side
no longer requires the semaphore, a one is written to cancel its re-
quest.
Semaphores are accessed by asserting SEM LOW. The SEM
pin functions as a chip select for the semaphore latches (CE must
remain HIGH during SEM LOW). A
address. OE and R/W are used in the same manner as a normal
memory access. When writing or reading a semaphore, the other
address pins have no effect.
When writing to the semaphore, only I/O
written to the left port of an available semaphore, a one will appear at
the same semaphore address on the right port. That semaphore can
now only be modified by the side showing zero (the left port in this
case). If the left port now relinquishes control by writing a one to the
semaphore, the semaphore will be set to one for both sides. Howev-
er, if the right port had requested the semaphore (written a zero) while
the left port had control, the right port would immediately own the
semaphore as soon as the left port released it. Table 3 shows sam-
ple semaphore operations.
When reading a semaphore, all sixteen/eighteen data lines
output the semaphore value. The read value is latched in an
output register to prevent the semaphore from changing state
during a write from the other port. If both ports attempt to ac-
cess the semaphore within t
definitely be obtained by one side or the other, but there is no guaran-
tee which side will control the semaphore.
SWRD
PS
of each other, the busy logic will determine which port has
PS
+ t
BLC
is violated, one port will definitely gain permission to the
DOE
or t
after the rising edge of the semaphore write. If the
BLA
BLA
), otherwise, the slave chip may begin a write
after an address match or t
SPS
of each other, the semaphore will
0–2
represents the semaphore
CY7C027/028
CY7C037/038
0
is used. If a zero is
Page 15 of 19
SOP
BLC
before at-
after CE