24C04A_04 Datasheet, PDF (9/14 Pages) Microchip Technology – 4K 5.0V I 2 C ™ Serial EEPROM

10.0 PIN DESCRIPTION
10.1 A0, A1, A2 Chip Address Inputs
A0 is not used as a chip select bit and must be tied to
either Vss or Vcc. The levels on the remaining two
address inputs(A1, A2) are compared with the corre-
sponding bits in the slave address. The chip is selected
if the compare is true. These inputs must be connected
to either VSS or VCC.
These two address inputs allow up to four 24C04A's
can be connected to the bus
10.2 SDA Serial Address/Data Input/Output
This is a bidirectional pin used to transfer addresses
and data into and data out of the device. It is an open
drain terminal, therefore the SDA bus requires a pull-up
resistor to VCC (typical 10KΩ).
For normal data transfer, SDA is allowed to change
only during SCL LOW. Changes during SCL HIGH are
reserved for indicating the START and STOP condi-
tions.
10.3 SCL Serial Clock
This input is used to synchronize the data transfer from
and to the device.
24C04A
10.4 WP Write Protection
This pin must be connected to either VCC or VSS. If tied
to VCC, write operations to the upper memory block will
not be executed. Read operations are possible.
If tied to VSS, normal memory operation is enabled
(read/write the entire memory).
This feature allows the user to assign the upper half of
the memory as ROM which can be protected against
accidental programming. When write is disabled, slave
address and word address will be acknowledged but
data will not be acknowledged.
Note 1: A “page” is defined as the maximum num-
ber of bytes that can be programmed in a
single write cycle. The 24C04A page is 8
bytes long.
Note 2: A “block” is defined as a continuous area
of memory with distinct boundaries. The
address pointer can not cross the bound-
ary from one block to another. It will how-
ever, wrap around from the end of a block
to the first location in the same block. The
24C04A has two blocks, 256 bytes each.
 2004 Microchip Technology Inc.
DS11183F-page 9