M24C16, M24C08, M24C04, M24C02, M24C01
Figure 8. Write Cycle Polling Flowchart using ACK
WRITE Cycle
in Progress
START Condition
DEVICE SELECT
with RW = 0
NO
First byte of instruction
with RW = 0 already
decoded by the device
ACK
Returned
YES
NO
Next
Operation is
Addressing the
Memory
YES
ReSTART
Send Address
and Receive ACK
STOP
NO
START
Condition
YES
DATA for the
WRITE Operation
DEVICE SELECT
with RW = 1
Continue the
WRITE Operation
Continue the
Random READ Operation
AI01847C
Minimizing System Delays by Polling On ACK
During the internal Write cycle, the device discon-
nects 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
to
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
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).
10/29
STMICROELECTRONICS [ STMICROELECTRONICS ]
