M24M02E-F datasheet(22/54 Pages) STMICROELECTRONICS

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6.2.6

Minimizing write delays by polling on ACK

During the internal write cycle, the device disconnects itself from the bus, and writes a copy of the data from its

internal latches to the memory cells. The maximum write time (tw) is shown in Table 19. AC characteristics in

Fast-mode and Table 20. AC characteristics in Fast-mode Plus, but the typical time is shorter. The bus controller

can implement a polling sequence to utilize this feature.

The sequence, as shown in Figure 16, is:

•

Initial condition: A write cycle is in progress.

•

Step 1: The bus controller issues a Start condition followed by a device select code (the first byte of the

new instruction).

•

Step 2: If the device is busy with the internal write cycle, NO ACK is returned and the bus controller goes

back to step 1. If the device has terminated the internal write cycle, it responds with an ACK, indicating that

the device is ready to receive the second part of the instruction (the first byte of this instruction having been

sent during step 1).

Note:

When writing a command to the configurable device address register when C2 is reconfigured, the device

returns ACK only if:

•

Chip enable address of the device select code is equal to the new C2 value.

•

An internal write cycle is completed (a new C2 has been programmed in the chip enable register).

Figure 16. Write cycle polling flowchart using ACK

Write cycle

in progress

operation is

addressing the

memory

Start condition

ACK

returned

YES

Re-start

Stop

Data for the

write operation

Send address

and receive ACK

YES

Continue the

write operation

Continue the

random read operation

Device select

with RW = 1

First byte of instruction

with RW = 0 already

decoded by the device

Device select

with RW = 0

StartCondition

1. The seven most significant bits of the device select code in a random read (bottom right box in the figure) must match those

of the device select code in the write operation (polling instruction in the figure).

M24M02E-F

Instructions

DS14157 - Rev 2

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