Device operation
Figure 8.
M24C16-125 M24C08-125 M24C04-125 M24C02-125
Write cycle polling flowchart using ACK
Write cycle
in progress
Start condition
Device select
with RW = 0
ACK
NO
Returned
First byte of instruction
YES
with RW = 0 already
decoded by the device
Next
operation is
addressing the
memory
NO
YES
Send Address
and Receive ACK
ReStart
Start
NO
YES
Stop
condition
Data for the
Write operation
Device select
with RW = 1
Continue the
Continue the
Random Read operation
Write operation
AI01847d
3.6.3
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 Write time (tw) is
shown in Table 9, 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 8, 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).
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STMICROELECTRONICS [ ST ]
