MCP79411 datasheet(20/38 Pages) MICROCHIP

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MCP7941X

DS22266B-page 20

Preliminary

 2011 Microchip Technology Inc.

5.2.4.3

Sequential Read

Sequential reads are initiated in the same way as a

random read except that after the MCP7941X transmits

the first data byte, the master issues an Acknowledge

as opposed to the Stop condition used in a random

read. This Acknowledge directs the MCP7941X to

transmit the next sequentially addressed 8-bit word

(Figure 5-3). Following the final byte transmitted to the

master, the master will NOT generate an Acknowledge

but will generate a Stop condition. To provide

sequential reads, the MCP7941X contains an internal

Address Pointer which is incremented by one at the

completion of each operation. This Address Pointer

allows the entire memory contents to be serially read

during one operation. The internal Address Pointer will

automatically roll over to the start of the Block.

FIGURE 5-2:

RANDOM READ (EEPROM SHOWN)

FIGURE 5-3:

SEQUENTIAL READ (EEPROM SHOWN)

5.3

Unique ID

The MCP7941X features an additional 64-bit unique ID

area. This is separate and in addition to the 1K of on-

board EEPROM.

The unique ID is located at addresses 0xF0 through

0xF7. Reading the unique ID requires the user to

simply address these bytes.

The unique ID area is protected to prevent unintended

writes to these locations. The unlock sequence is

detailed in 4.2.2 “Unlock Sequence”.

The unique ID can be factory programmed on some

devices to provide a unique IEEE EUI-48 or EUI-64

value. In addition, customer-provided codes can also

be programmed.

BUS ACTIVITY

MASTER

SDA LINE

BUS ACTIVITY

CONTROL

BYTE

ADDRESS

BYTE

CONTROL

BYTE

DATA

BYTE

S 1 010

111

S 10 10

BUS ACTIVITY

MASTER

SDA LINE

BUS ACTIVITY

CONTROL

BYTE

DATA n

DATA n + 1

DATA n + 2

DATA n + X

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