ADT7461

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12

Table 13. LIST OF REGISTERS

Read Address (Hex)

Write Address (Hex)

Name

Power-On Default

Not Applicable

Not Applicable

Address Pointer

Undefined

0x00

Not Applicable

Local Temperature Value

0000 0000 (0x00)

0x01

Not Applicable

External Temperature Value High Byte

0000 0000 (0x00)

0x02

Not Applicable

Status

Undefined

0x03

0x09

Configuration

0000 0000 (0x00)

0x04

0x0A

Conversion Rate

0000 1000 (0x08)

0x05

0x0B

Local Temperature High Limit

0101 0101 (0x55) (85°C)

0x06

0x0C

Local Temperature Low Limit

0000 0000 (0x00) (0°C)

0x07

0x0D

External Temperature High Limit High Byte

0101 0101 (0x55) (85°C)

0x08

0x0E

External Temperature Low Limit High Byte

0000 0000 (0x00) (0°C)

Not Applicable

0x0F (Note 1)

One-Shot

0x10

Not Applicable

External Temperature Value Low Byte

0000 0000

0x11

0x11

External Temperature Offset High Byte

0000 0000

0x12

0x12

External Temperature Offset Low Byte

0000 0000

0x13

0x13

External Temperature High Limit Low Byte

0000 0000

0x14

0x14

External Temperature Low Limit Low Byte

0000 0000

0x19

0x19

External THERM Limit

0110 1100 (0x55) (85°C)

0x20

0x20

Local THERM Limit

0101 0101 (0x55) (85°C)

0x21

0x21

THERM Hysteresis

0000 1010 (0x0A) (10°C)

0x22

0x22

Consecutive ALERT

0000 0001 (0x01)

0xFE

Not Applicable

Manufacturer ID

0100 0001 (0x41)

0xFF

Not Applicable

Die Revision Code

0101 0001 (0x51)

1. Writing to Address ox0F causes the ADT7461 to perform a single measurement. It is not a data register, therefore, data written to it is

irrelevant.

Serial Bus Interface

Control of the ADT7461 is carried out via the serial bus.

The ADT7461 is connected to this bus as a slave device,

under the control of a master device.

After a conversion sequence completes, there should be

no SMBus transactions to the ADT7461 for at least one

conversion time, to allow the next conversion to complete.

The conversion time depends on the value programmed in

the conversion rate register.

The ADT7461 has an SMBus timeout feature. When this

is enabled, the SMBus times out typically after 25 ms of

inactivity. However, this feature is not enabled by default.

Bit 7 of the consecutive alert register (Address = 0x22)

should be set to enable it.

Consult the SMBus 1.1 specification for more

Addressing the Device

In general, every SMBus device has a 7-bit device

address, except for some devices that have extended 10-bit

addresses. When the master device sends a device address

over the bus, the slave device with that address responds.

The ADT7461 is available with one device address, 0x4C

(1001 100b). The ADT7461-2 is also available with one

device address, 0x4D (1001 101b)

The serial bus protocol operates as follows:

1. The master initiates data transfer by establishing a

start condition, defined as a high-to-low transition

on the serial data line SDATA, while the serial

clock line SCLK remains high. This indicates that

an address/data stream will follow. All slave

peripherals connected to the serial bus respond to

the start condition and shift in the next eight bits,

consisting of a 7-bit address (MSB first) plus an

R/W bit, which determines the direction of the

data transfer, that is, whether data will be written

to or read from the slave device. The peripheral

whose address corresponds to the transmitted

address responds by pulling the data line low

during the low period before the ninth clock pulse,

known as the acknowledge bit. All other devices

on the bus now remain idle while the selected

device waits for data to be read from or written to

it. If the R/W bit is a 0, the master writes to the

slave device. If the R/W bit is a 1, the master reads

from the slave device.

2. Data is sent over the serial bus in a sequence of

nine clock pulses, eight bits of data followed by an

acknowledge bit from the slave device. Transitions

on the data line must occur during the low period