X24C04 datasheet(5/18 Pages) XICOR

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X24C04

DEVICE ADDRESSING

Following a start condition the master must output the

address of the slave it is accessing. The most significant

four bits of the slave are the device type identifier (see

Figure 4). For the X24C04 this is fixed as 1010[B].

The last bit of the slave address defines the operation to

be performed. When set to one a read operation is

selected, when set to zero a write operation is selected.

Following the start condition, the X24C04 monitors the

SDA bus comparing the slave address being transmit-

ted with its slave address (device type and state of A1

and A2 inputs). Upon a correct compare the X24C04

outputs an acknowledge on the SDA line. Depending on

the state of the R/

W bit, the X24C04 will execute a read

or write operation.

WRITE OPERATIONS

Byte Write

For a write operation, the X24C04 requires a second

address field. This address field is the word address,

comprised of eight bits, providing access to any one of the

512 words of memory. Upon receipt of the word address

the X24C04 responds with an acknowledge, and awaits

the next eight bits of data, again responding with an

acknowledge. The master then terminates the transfer by

generating a stop condition, at which time the X24C04

begins the internal write cycle to the nonvolatile memory.

While the internal write cycle is in progress the X24C04

inputs are disabled, and the device will not respond to any

requests from the master. Refer to Figure 5 for the

address, acknowledge and data transfer sequence.

Figure 4. Slave Address

3839 FHD F09

The next two significant bits address a particular device.

A system could have up to four X24C04 devices on the

bus (see Figure 10). The four addresses are defined by

the state of the A1 and A2 inputs.

The next bit of the slave address is an extension of the

array’s address and is concatenated with the eight bits

of address in the word address field, providing direct

access to the whole 512 x 8 array.

Figure 5. Byte Write

BUS ACTIVITY:

MASTER

SDA LINE

BUS ACTIVITY:

X24C04

SLAVE

ADDRESS

WORD

ADDRESS

DATA

3839 FHD F10

R/W

DEVICE TYPE

IDENTIFIER

DEVICE

ADDRESS

HIGH

ORDER

WORD

ADDRESS

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