M34D64-W Device operation
13/27
3.5 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 Device Select Code,
shown in Table 2.: Device select code (on Serial Data (SDA), most significant bit first).
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
1010b.
Up to eight memory devices can be connected on a single I
2
C bus. Each one is given a
unique 3-bit code on the Chip Enable (E0, E1, E2) inputs. When the Device Select Code is
received on Serial Data (SDA), the device only responds if the Chip Enable Address is the
same as the value on the Chip Enable (E0, E1, E2) inputs.
The 8
th
bit is the Read/Write bit (RW). This bit is set to 1 for Read and 0 for Write operations.
If a match occurs on the Device Select code, the corresponding device gives an
acknowledgment on Serial Data (SDA) during the 9
th
bit time. If the device does not match
the Device Select code, it deselects itself from the bus, and goes into Standby mode.
Table 5. Operating modes
Mode RW bit WC
(1)
1. X = V
IH
or V
IL
.
Bytes Initial sequence
Current Address Read 1 X 1 Start, Device Select, RW
= 1
Random Address Read
0X
1
Start, Device Select, RW
= 0, Address
1 X reStart, Device Select, RW
= 1
Sequential Read 1 X ≥ 1
Similar to Current or Random Address
Read
Byte Write 0 V
IL
1 Start, Device Select, RW = 0
Page Write 0 V
IL
≤ 32 Start, Device Select, RW = 0
