11AA02UID datasheet(11/32 Pages) MICROCHIP

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DS20005206A-page 11

11AA02UID

4.3

Write Instruction

Prior to any attempt to write data to the 11AA02UID, the

write enable latch must be set by issuing the

WREN

instruction (see Section 4.4 “Write Enable (WREN)

and Write Disable (WRDI) Instructions”).

Once the write enable latch is set, the user may

proceed with issuing a

WRITE instruction (including

the header and device address bytes) followed by the

MSB and LSB of the Word Address. Once the last

Acknowledge sequence has been performed, the

master transmits the data byte to be written.

The 11AA02UID features a 16-byte page buffer, mean-

ing that up to 16 bytes can be written at one time. To

utilize this feature, the master can transmit up to 16

data bytes to the 11AA02UID, which are temporarily

stored in the page buffer. After each data byte, the

master sends a MAK, indicating whether or not another

data byte is to follow. A NoMAK indicates that no more

data is to follow, and as such will initiate the internal

write cycle.

Upon receipt of each word, the four lower-order

Address Pointer bits are internally incremented by one.

The higher-order bits of the word address remain con-

stant. If the master should transmit data past the end of

the page, the address counter will roll over to the begin-

ning of the page, where further received data will be

written.

FIGURE 4-3:

WRITE COMMAND SEQUENCE

Note:

If a NoMAK is generated before any data

has been provided, or if a standby pulse

occurs before the NoMAK is generated,

the 11AA02UID will be reset, and the write

cycle will not be initiated.

Note:

Page write operations are limited to writ-

ing bytes within a single physical page,

regardless of the number of bytes actu-

ally being written. Physical page boundar-

ies start at addresses that are integer

multiples of the page size (16 bytes) and

end at addresses that are integer multi-

ples of the page size minus 1. As an

example, the page that begins at address

0x30 ends at address 0x3F. If a page

Write command attempts to write across a

physical page boundary, the result is that

the data wraps around to the beginning of

the current page (overwriting data previ-

ously stored there), instead of being writ-

ten to the next page as might be expected.

It is therefore necessary for the applica-

tion software to prevent page write opera-

tions that would attempt to cross a page

boundary.

76 5 4

Data Byte 1

32 1 0

76 5 4

Data Byte 2

32 1 0

76 5 4

Data Byte n

32 1 0

SCIO

Start Header

SCIO

Device Address

Command

Standby Pulse

SCIO

15 14 13 12

Word Address MSB

11 10 9 8

76 5 4

Word Address LSB

32 1 0

Twc

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