MAX6875 データシートの表示（PDF） - Maxim Integrated

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MAX6875

EEPROM-Programmable, Hex/Quad, Power-Supply Sequencers/Supervisors

Maxim Integrated 

EEPROM-Programmable, Hex/Quad,

Power-Supply Sequencers/Supervisors

Send Byte

The send byte protocol allows the master device to send

one byte of data to the slave device (see Figure 7). The

send byte presets a register pointer address for a sub-

sequent read or write. The slave sends a NACK instead

of an ACK if the master tries to send an address that is

not allowed. If the master sends 80h, 81h, or 82h, the

data is ACK. This could be start of the write byte/word

protocol, and the slave expects at least one further

data byte. If the master sends a stop condition, the

internal address pointer does not change. If the master

sends 84h, this signifies that the block read protocol is

expected, and a repeated start condition should follow.

The device reboots if the master sends 88h. The send

byte procedure follows:

1) The master sends a start condition.

2) The master sends the 7-bit slave address and a

write bit (low).

3) The addressed slave asserts an ACK on SDA.

4) The master sends an 8-bit data byte.

5) The addressed slave asserts an ACK on SDA.

6) The master sends a stop condition.

Write Byte/Word

The write byte/word protocol allows the master device

to write a single byte in the register bank, preset an

EEPROM (configuration or user) address for a subse-

quent read, or to write a single byte to the configuration

or user EEPROM (see Figure 7). The write byte/word

procedure follows:

1) The master sends a start condition.

2) The master sends the 7-bit slave address and a

write bit (low).

3) The addressed slave asserts an ACK on SDA.

4) The master sends an 8-bit command code.

5) The addressed slave asserts an ACK on SDA.

6) The master sends an 8-bit data byte.

7) The addressed slave asserts an ACK on SDA.

8) The master sends a stop condition or sends another

8-bit data byte.

9) The addressed slave asserts an ACK on SDA.

10) The master sends a stop condition.

To write a single byte to the register bank, only the 8-bit

command code and a single 8-bit data byte are sent.

The command code must be in the range of 00h to 45h.

The data byte is written to the register bank if the com-

mand code is valid. The slave generates a NACK at

step 5 if the command code is invalid.

To preset an EEPROM (configuration or user) address

for a subsequent read, the 8-bit command code and a

single 8-bit data byte are sent. The command code

must be 80h if the write is to be directed into the config-

uration EEPROM, or 81h or 82h, if the write is to be

directed into the user EEPROM. If the command code is

80h, the data byte must be in the range of 00h to 45h. If

the command code is 81h or 82h, the data byte can be

00h to FFh. A NACK is generated in step 7 if none of the

above conditions are true.

To write a single byte of data to the user or configuration

EEPROM, the 8-bit command code and a single 8-bit

data byte are sent. The following 8-bit data byte is writ-

ten to the addressed EEPROM location.

SDA

1

0

1

0

A1

A0

X

R/W

ACK

(0)

START

MSB

LSB

SCL

(MAX6875 ONLY)

Figure 6. Slave Address

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