Device operation M24C16, M24C08, M24C04, M24C02, M24C01
16/40 Doc ID 5067 Rev 13
Figure 9. Write cycle polling flowchart using ACK
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 (t
w
) is
shown in Table 15, 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).
Write cycle
in progress
AI01847d
Next
operation is
addressing the
memory
Start condition
Device select
with RW = 0
ACK
Returned
YES
NO
YESNO
ReStart
Stop
Data for the
Write operation
Device select
with RW = 1
Send Address
and Receive ACK
First byte of instruction
with RW = 0 already
decoded by the device
YESNO
Start
condition
Continue the
Write operation
Continue the
Random Read operation
M24C16, M24C08, M24C04, M24C02, M24C01 Device operation
Doc ID 5067 Rev 13 17/40
Figure 10. Read mode sequences
1. The seven most significant bits of the device select code of a Random Read (in the 1
st
and 3
rd
bytes) must
be identical.
3.7 Read operations
Read operations are performed independently of the state of the Write Control (WC) signal.
The device has an internal address counter which is incremented each time a byte is read.
3.7.1 Random Address Read
A dummy Write is first performed to load the address into this address counter (as shown in
Figure 10) but without sending a Stop condition. Then, the bus master sends another Start
condition, and repeats the device select code, with the Read/Write bit (RW) set to 1. The
device acknowledges this, and outputs the contents of the addressed byte. The bus master
must not acknowledge the byte, and terminates the transfer with a Stop condition.
Start
Dev select * Byte address
Start
Dev select Data out 1
AI01942b
Data out N
Stop
Start
Current
Address
Read
Dev select Data out
Random
Address
Read
Stop
Start
Dev select * Data out
Sequentila
Current
Read
Stop
Data out N
Start
Dev select * Byte address
Sequential
Random
Read
Start
Dev select * Data out 1
Stop
ACK
R/W
NO ACK
ACK
R/W
ACK ACK
R/W
ACK ACK ACK NO ACK
R/W
NO ACK
ACK ACK
R/W
ACK ACK
R/W
ACK NO ACK
Device operation M24C16, M24C08, M24C04, M24C02, M24C01
18/40 Doc ID 5067 Rev 13
3.7.2 Current Address Read
For the Current Address Read operation, following a Start condition, the bus master only
sends a device select code with the Read/Write bit (RW) set to 1. The device acknowledges
this, and outputs the byte addressed by the internal address counter. The counter is then
incremented. The bus master terminates the transfer with a Stop condition, as shown in
Figure 10, without acknowledging the byte.
3.7.3 Sequential Read
This operation can be used after a Current Address Read or a Random Address Read. The
bus master does acknowledge the data byte output, and sends additional clock pulses so
that the device continues to output the next byte in sequence. To terminate the stream of
bytes, the bus master must not acknowledge the last byte, and must generate a Stop
condition, as shown in Figure 10.
The output data comes from consecutive addresses, with the internal address counter
automatically incremented after each byte output. After the last memory address, the
address counter ‘rolls-over’, and the device continues to output data from memory address
00h.
3.7.4 Acknowledge in Read mode
For all Read commands, the device waits, after each byte read, for an acknowledgment
during the 9
th
bit time. If the bus master does not drive Serial Data (SDA) Low during this
time, the device terminates the data transfer and switches to its Standby mode.

M24C02-RDS6G

Mfr. #:
Manufacturer:
STMicroelectronics
Description:
EEPROM 1.8-5.5V 2K (256x8)
Lifecycle:
New from this manufacturer.
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