CY15B004J
operation is complete. This is explained in more detail in the
interface section.
Functional Overview
The CY15B004J is a serial F-RAM memory. The memory array
is logically organized as 512 × 8 bits and is accessed using an
industry-standard I2C interface. The functional operation of the
F-RAM is similar to serial (I2C) EEPROM. The major difference
between the CY15B004J and a serial (I2C) EEPROM with the
same pinout is the F-RAM's superior write performance, high
endurance, and low power consumption.
Note that the CY15B004J contains no power management
circuits other than a simple internal power-on reset. It is the
user’s responsibility to ensure that VDD is within data sheet
tolerances to prevent incorrect operation.
2
I C Interface
The CY15B004J employs a bi-directional I2C bus protocol using
few pins or board space. Figure 2 illustrates a typical system
configuration using the CY15B004J in a microcontroller-based
system. The industry standard I2C bus is familiar to many users
but is described in this section.
Memory Architecture
When accessing the CY15B004J, the user addresses 512
locations of eight data bits each. These eight data bits are shifted
in or out serially. The addresses are accessed using the I2C
protocol, which includes a slave address (to distinguish other
non-memory devices), a page address bit, and a word address.
The word address consists of 8-bits that specify one of the 256
addresses. The page address is 1-bit and so there are 2 pages
of 256 locations. The complete address of 9-bits specifies each
byte address uniquely.
By convention, any device that is sending data onto the bus is
the transmitter while the target device for this data is the receiver.
The device that is controlling the bus is the master. The master
is responsible for generating the clock signal for all operations.
Any device on the bus that is being controlled is a slave. The
CY15B004J is always a slave device.
The bus protocol is controlled by transition states in the SDA and
SCL signals. There are four conditions including START, STOP,
data bit, or acknowledge. Figure 3 on page 5 and Figure 4 on
page 5 illustrates the signal conditions that specify the four
states. Detailed timing diagrams are shown in the electrical
specifications section.
The access time for the memory operation is essentially zero,
beyond the time needed for the serial protocol. That is, the
memory is read or written at the speed of the I2C bus. Unlike a
serial (I2C) EEPROM, it is not necessary to poll the device for a
ready condition because writes occur at bus speed. By the time
a new bus transaction can be shifted into the device, a write
Figure 2. System Configuration using Serial (I2C) nvSRAM
Vcc
R
R
= (V - V max) / I
DD OL OL
Pmin
= t / (0.8473 * C )
Pmax
r
b
SDA
SCL
Microcontroller
Vcc
Vcc
A1
A2
SCL
SDA
A1
A2
SCL
SDA
A1
A2
SCL
SDA
WP
WP
WP
#1
#0
#3
STOP Condition (P)
START Condition (S)
A STOP condition is indicated when the bus master drives SDA
from LOW to HIGH while the SCL signal is HIGH. All operations
using the CY15B004J should end with a STOP condition. If an
operation is in progress when a STOP is asserted, the operation
will be aborted. The master must have control of SDA in order to
assert a STOP condition.
A START condition is indicated when the bus master drives SDA
from HIGH to LOW while the SCL signal is HIGH. All commands
should be preceded by a START condition. An operation in
progress can be aborted by asserting a START condition at any
time. Aborting an operation using the START condition will ready
the CY15B004J for a new operation.
If during operation the power supply drops below the specified
V
DD minimum, the system should issue a START condition prior
to performing another operation.
Document Number: 002-10549 Rev. *C
Page 4 of 18
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