24C04A-ESM datasheet(9/12 Pages) MICROCHIP

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DS11183E-page 9

24C04A

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 10K

Ω).

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.

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.

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