Device operation

M34E04B

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DocID028428 Rev 1

Up to eight memory devices can be connected on a single serial bus. Each one is given a

unique 3-bit code on the slave address (SA2, SA1, SA0) inputs. When the device select

code is received, the device only responds if the slave address is the same as the value on

the slave address (SA2, SA1, SA0) inputs.

If a match occurs on the device select code, the corresponding device gives an

the device select code, it deselects itself from the bus, and goes into Standby mode.

3.6

Write operations

Following a Start condition, the bus master sends a device select code with the RW bit reset

to 0. The device acknowledges this, as shown in Figure 5, and waits for an address byte.

Table 2. Device Type Identifier Code (DTIC)

Abbr

Device type identifier

(1)

Select address

(2) (3)

R_W_n

SA0 pin

(4)

b7

b6

b5

b4

b3

b2

b1

b0

Read

RSPD

1

0

1

0

LSA2 LSA1 LSA0

1

0 or 1

Write

WSPD

0

Set Write Protection, block 0

SWP0

011

0

001

0

Set Write Protection, block 1

SWP1

1

0

0

0

Set Write Protection, block 2

SWP2

1

0

1

0

Set Write Protection, block 3

SWP3

0

0

0

0

Clear All Write Protection

CWP

0

1

1

0

0

0

1

1

Read Protection Status, block 1 (5) RPS1

1

0

0

1

Read Protection Status, block 2 (5) RPS2

1

0

1

1

Read Protection Status, block 3 (5) RPS3

0

0

0

1

SPA0

1

1

0

0

Set Page Address to 1 (6)

SPA1

1

1

1

0

RPA

110

1

Reserved

-

All other encodings

1. The most significant bit, b7, is sent first.

2. Logical Serial Addresses (LSA) are generated by the combination of inputs on the SA pins.

3. For backward compatibility with M34E02 devices, the order of block select bits (b3 and b1) is not a simple binary encoding

of the block number.

4. SA0 pin is driven to Vss, Vcc or VHV.

5. Reading the block protection status results in Ack.

6. Setting the EE page address to 0 selects the lower 256 bytes of EEPROM; setting it to 1 selects the upper 256 bytes of

EEPROM. Subsequent Read EE or Write EE commands operate on the selected EE page.

7. Reading the EE page address results in Ack when the current page is 0, and NoAck when the current page is 1.