24C04 datasheet(9/16 Pages) STMICROELECTRONICS

9 / 16 page

ory address bits (A7-A3) are the same inside one

block. The master sends from one up to 8 bytes of

data, which are each acknowledged by the mem-

ory. After each byte is transfered, the internal byte

address counter (3 least significant bits only) is

incremented. The transfer is terminated by the

master generating a STOP condition. Care must be

taken to avoid address counter ’roll-over’ which

could result in data being overwritten. Note that, for

any write mode, the generation by the master of the

STOP condition starts the internal memory pro-

gram cycle. All inputs are disabled until the comple-

tion of this cycle and the memory will not respond

to any request.

Minimizing System Delays by Polling On ACK.

During the internal write cycle, the memory discon-

nects itself from the bus in order to copy the data

from the internal latches to the memory cells. The

maximum value of the write time (tW) is given in the

AC Characteristics table, since the typical time is

shorter, the time seen by the system may be re-

duced by an ACK polling sequence issued by the

master.

WRITE Cycle

in Progress

AI01099B

Operation is

Addressing the

Memory

START Condition

DEVICE SELECT

with RW = 0

ACK

Returned

YES

ReSTART

STOP

Proceed

WRITE Operation

Proceed

Random Address

READ Operation

Send

Byte Address

First byte of instruction

with RW = 0 already

decoded by ST24xxx

Figure 8. Write Cycle Polling using ACK

AI00855B

1FFh

b3 b2

100h

Block 1

Block 0

Protect Flag

Enable = 0

Disable = 1

8 byte

boundary

address

Protect Location

Figure 7. Memory Protection

9/16

ST24/25C04, ST24/25W04

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