24C32A, 24C64A
PIN DESCRIPTIONS
(A) SERIAL CLOCK (SCL)
The rising edge of this SCL input is to latch data into the EEPROM device while the falling edge of this clock is to
clock data out of the EEPROM device.
(B) DEVICE / CHIP SELECT ADDRESSES (A2, A1, A0)
These are the chip select input signals for the serial EEPROM devices. Typically, these signals are hardwired to
either V
IH
or V
IL
. If left unconnected, they are internally recognized as V
IL
.
(C) SERIAL DATA LINE (SDA)
SDA data line is a bi-directional signal for the serial devices. It is an open drain output signal and can be wired-
OR with other open-drain output devices.
(D) WRITE PROTECT (WP)
The FT24C32A/64A devices have a WP pin to protect the whole EEPROM array from programming.
Programming operations are allowed if WP pin is left un-connected or input to V
IL
. Conversely all programming
functions are disabled if WP pin is connected to V
IH
or V
CC
. Read operations is not affected by the WP pin’s input
level.
MEMORY ORGANIZATION
The FT24C32A/64A devices have 128/256 pages respectively. Since each page has 32 bytes, random word addressing
to FT24C32A/64A will require 12/13 bits data word addresses respectively.
DEVICE OPERATION
(A) SERIAL CLOCK AND DATA TRANSITIONS
The SDA pin is typically pulled to high by an external resistor. Data is allowed to change only when Serial clock
SCL is at V
IL
. Any SDA signal transition may interpret as either a START or STOP condition as described below.
(B) START CONDITION
With SCL ≥V
IH
, a SDA transition from high to low is interpreted as a START condition. All valid commands
must begin with a START condition.
(C) STOP CONDITION
With SCL ≥V
IH
, a SDA transition from low to high is interpreted as a STOP condition. All valid read or write
commands end with a STOP condition. The device goes into the STANDBY mode if it is after a read command.
A STOP condition after page or byte write command will trigger the chip into the STANDBY mode after the self-
timed internal programming finish (see Figure 1).
(D) ACKNOWLEDGE
The 2-wire protocol transmits address and data to and from the EEPROM in 8 bit words. The EEPROM
acknowledges the data or address by outputting a "0" after receiving each word. The ACKNOWLEDGE signal
occurs on the 9
th
serial clock after each word.
© 2009 Fremont Micro Devices Inc. DS3005J-page3
