ST25DV04K datasheet(92/220 Pages) STMICROELECTRONICS

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I2C operation

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DocID027603 Rev 4

Figure 27. Write mode sequences when write is inhibited

Note:

N ≤ 256

6.4.3

Minimizing system 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 I²C write time (tw) is

shown in Table 209: I2C AC characteristics up to 85°C and Table 210: I2C AC

characteristics up to 125°C, but the typical time is shorter. To make use of this, a polling

sequence can be used by the bus master.

The sequence, as shown in Figure 28: Write cycle polling flowchart using ACK, is:

•

Initial condition: a write cycle is in progress.

•

Step 1: the bus master 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

master 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:

There is no need of polling when writing in dynamic registers or in mailbox, since

programming time is null.

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