M34A02 Datasheet, PDF (4/15 Pages) STMicroelectronics – 2 Kbit Serial SMBus EEPROM for ACR Card Configuration

M34A02
Figure 5. ACR Serial Bus Protocol
SCL
SDA
START
Condition
SDA
Input
SDA
Change
STOP
Condition
SCL
SDA
1
2
3
MSB
START
Condition
7
8
9
ACK
SCL
SDA
1
2
3
MSB
7
8
9
ACK
STOP
Condition
AI00792B
For correct device operation, Serial Data (SDA)
must be stable before the rising edge of Serial
Clock (SCL), and the data must change only after
Serial Clock (SCL) is Low.
Memory Addressing
To start communication between the bus master
and the slave device, the bus master must initiate
a Start condition. Following this, the bus master
sends the 8-bit byte, shown in Table 3, on Serial
Data (SDA) (most significant bit first). This
consists of the 7-bit Device Select code, and the
Read/Write bit (RW).
The Device Select Code consists of a 4-bit Device
Type Identifier, and a 3-bit Chip Enable “Address”
(E2, E1, E0). To address the memory array, the 4-
bit Device Type Identifier is 1011b.
Up to eight memory devices can be connected on
a single bus. Each one is given a unique 3-bit code
on Chip Enable (E0, E1, E2). When the Device
Select Code is received on Serial Data (SDA), the
device only responds if the Chip Select Code is the
Table 3. Device Select Code ¹
Device Type Identifier
b7
b6
b5
b4
Device Select Code
1
0
1
1
Note: 1. The most significant bit, b7, is sent first.
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Chip Enable
RW
b3
b2
b1
b0
E2
E1
E0
RW