ADM1026JSTZ-R7 datasheet(14/55 Pages) ONSEMI

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ADM1026

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In the ADM1026, the write byte/word protocol is used for

four purposes. The ADM1026 knows how to respond by the

value of the command byte and EEPROM Register 3.

The first purpose is to write a single byte of data to RAM.

In this case, the command byte is the RAM address from 00h

to 6Fh and the (only) data byte is the actual data. This is

illustrated in Figure 19.

Figure 19. Single Byte Write to RAM

SLAVE

ADDRESS

RAM

ADDRESS

(00h TO 6Fh)

A DATA AP

The protocol is also used to set up a 2-byte EEPROM

address for a subsequent read or block read. In this case, the

command byte is the high byte of the EEPROM address

from 80h to 9Fh. The (only) data byte is the low byte of the

EEPROM address. This is illustrated in Figure 20.

Figure 20. Setting an EEPROM Address

SLAVE

ADDRESS W

EEPROM

ADDRESS

HIGH BYTE

(80h TO 9Fh)

EEPROM

ADDRESS

LOW BYTE

(00h TO FFh)

If it is required to read data from the EEPROM

immediately after setting up the address, the master can

assert a repeat start condition immediately after the final

ACK and carry out a single-byte read or block read operation

without asserting an intermediate stop condition. In this

case, Bit 0 of EEPROM Register 3 should be set.

The third use is to erase a page of EEPROM memory.

EEPROM memory can be written to only if it is previously

erased. Before writing to one or more EEPROM memory

locations that are already programmed, the page or pages

containing those locations must first be erased. EEPROM

memory is erased by writing an EEPROM page address plus

an arbitrary byte of data with Bit 2 of EEPROM Register 3

set to 1.

Because the EEPROM consists of 128 pages of 64 bytes,

the EEPROM page address consists of the EEPROM

address high byte (from 80h to 9Fh) and the two MSBs of the

low byte. The lower six bits of the EEPROM address (low

byte only) specify addresses within a page and are ignored

during an erase operation.

Figure 21. EEPROM Page Erasure

SLAVE

ADDRESS WA

EEPROM

ADDRESS

HIGH BYTE

(80h TO 9Fh)

A ARBITRARY

DATA

EEPROM

ADDRESS

LOW BYTE

(00h TO FFh)

9 10

A Y

Page erasure takes approximately 20 ms. If the EEPROM

is accessed before erasure is complete, the ADM1026

responds with No Acknowledge.

Last, this protocol is used to write a single byte of data to

EEPROM. In this case, the command byte is the high byte

of the EEPROM address from 80h to 9Fh. The first data byte

is the low byte of the EEPROM address, and the second data

byte is the actual data. Bit 1 of EEPROM Register 3 must be

set. This is illustrated in Figure 22.

Figure 22. Single-Byte Write to EEPROM

SLAVE

ADDRESS

EEPROM

ADDRESS

HIGH BYTE

(80h TO 9Fh)

A DATA

EEPROM

ADDRESS

LOW BYTE

(00h TO FFh)

910

Block Write

In this operation, the master device writes a block of data

to a slave device. The start address for a block write must

have been set previously. In the case of the ADM1026, this

is done by a Send Byte operation to set a RAM address or by

a write byte/word operation to set an EEPROM address.

1. The master device asserts a start condition on the

SDA.

2. The master sends the 7-bit slave address followed

by the write bit (low).

3. The addressed slave device asserts an ACK on the

SDA.

4. The master sends a command code that tells the

slave device to expect a block write. The

ADM1026 command code for a block write is A0h

(10100000).

5. The slave asserts an ACK on the SDA.

6. The master sends a data byte (20h) that tells the

slave device that 32 data bytes are being sent to it.

The master should always send 32 data bytes to

the ADM1026.

7. The slave asserts an ACK on the SDA.

8. The master sends 32 data bytes.

9. The slave asserts an ACK on the SDA after each

data byte.

10. The master sends a packet error checking (PEC)

byte.

11. The ADM1026 checks the PEC byte and issues an

ACK if correct. If incorrect (NACK), the master

resends the data bytes.

12. The master asserts a stop condition on the SDA to

end the transaction.

Figure 23. Block Write to EEPROM or RAM

S SLAVE

ADDRESS WA

COMMAND

A0h BLOCK

WRITE

A DATA 1

BYTE

COUNT

AA P

DATA 2 A DATA

PEC

When performing a block write to EEPROM, Bit 1 of

EEPROM Register 3 must be set. Unlike some EEPROM

devices that limit block writes to within a page boundary,

there is no limitation on the start address when performing

a block write to EEPROM, except:

 There must be at least 32 locations from the start

address to the highest EEPROM address (9FF) to avoid

writing to invalid addresses.

 If the addresses cross a page boundary, both pages must

be erased before programming.

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