Datasheet

Instructions M24M02-DR
18/36 DocID18204 Rev 6
5.1.6 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 (t
w
) is
shown in AC characteristics tables in Section 8: DC and AC parameters, 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 9, 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 will be 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).
Figure 9. Write cycle polling flowchart using ACK
1. The seven most significant bits of the Device Select code of a Random Read (bottom right box in the
figure) must be identical to the seven most significant bits of the Device Select code of the Write (polling
instruction in the figure).
Write cycle
in progress
AI
01847
d
AI01847e
Next
Operation is
addressing the
memory
Start condition
Device select
with RW = 0
ACK
returned
YES
NO
YESNO
ReStart
Stop
Data for the
Write cperation
Device select
with RW = 1
Send Address
and Receive ACK
First byte of instruction
with RW = 0 already
decoded by the device
YESNO
StartCondition
Continue the
Write operation
Continue the
Random Read operation