ADM1032

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12

Figure 13. Writing a Register Address to the Address Pointer Register,

then Writing Data to the Selected Register

Figure 14. Writing to the Address Pointer Register Only

Figure 15. Reading Data from a Previously Selected Register

A6

11

9

A5

A4

A3

A2

A1

A0

R/W

D7

D6

D5

D4

D3

D2

D1

D0

SCLK

SDATA

START BY

MASTER

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

ADDRESS POINTER REGISTER BYTE

STOP BY

MASTER

ACK. BY

ADM1032

ACK. BY

ADM1032

FRAME 3

DATA BYTE

SDATA (CONTINUED)

SCLK (CONTINUED)

ACK. BY

ADM1032

9

1

D7

D6

D5

D4

D3

D2

D1

D0

9

SCLK

SDATA

START BY

MASTER

11

9

A6

A5

A4

A3

A2

A1

A0

R/W

D7

D6

D5

D4

D3

D2

D1

D0

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

ADDRESS POINTER REGISTER BYTE

STOP BY

MASTER

ACK. BY

ADM1032

ACK. BY

ADM1032

9

SCLK

19

1

9

SDATA

A6

A5

A4

A3

A2

A1

A0

R/W

D7

D6

D5

D4

D3

D2

D1

D0

START BY

MASTER

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

DATA BYTE FROM ADM1032

STOP BY

MASTER

ACK. BY

ADM1032

ACK. BY

ADM1032

ALERT Output

The ALERT output goes low whenever an out−of−limit

measurement is detected, or if the remote temperature sensor

is open−circuit. It is an open drain and requires a pullup to

so that the common line goes low if one or more of the

ALERT outputs goes low.

The ALERT output can be used as an interrupt signal to a

processor, or it can be used as an SMBALERT. Slave devices

on the SMBus can not normally signal to the master that they

want to talk, but the SMBALERT function allows them to do

so.

One or more ALERT outputs can be connected to a

common SMBALERT line connected to the master. When

the SMBALERT line is pulled low by one of the devices, the

following procedure occurs (see Figure 16).

Figure 16. Use of SMBALERT

ALERT RESPONSE

ADDRESS

MASTER SENDS

ARA AND READ

COMMAND

DEVICE SENDS

ITS ADDRESS

RD

START

ACK

DEVICE

ADDRESS

NO

ACK STOP

MASTER

RECEIVES

SMBALERT

1. SMBALERT is pulled low.

2. Master initiates a read operation and sends the

alert response address (ARA = 0001 100). This is

a general call address that must not be used as a

specific device address.

3. The device whose ALERT output is low responds

to the alert response address and the master reads

its device address. Since the device address is