MCP9808 datasheet(16/52 Pages) MICROCHIP

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MCP9808

DS25095A-page 16

5.1

Registers

The

MCP9808

has

several

registers

that

are

user-accessible. These registers include the Tempera-

ture register, Configuration register, Temperature Alert

Upper Boundary and Lower Boundary Limit registers,

Critical

Temperature

Limit

Manufacturer

Identification register and Device Identification register.

The Temperature register is read-only, used to access

the ambient temperature data. This register is double-

buffered and it is updated every tCONV. The Temperature

Alert Upper Boundary and Lower Boundary Limit

registers are read/write registers. If the ambient

temperature drifts beyond the user-specified limits, the

MCP9808 outputs a signal using the Alert pin (refer to

Section 5.2.3 “Alert Output Configuration”). In

addition, the Critical Temperature Limit register is used

to provide an additional critical temperature limit.

The

Configuration

provides

access

configure the MCP9808 device’s various features.

These registers are described in further detail in the

following sections.

The registers are accessed by sending a Register

Pointer to the MCP9808, using the serial interface. This

is an 8-bit write-only pointer. However, the four Least

Significant bits are used as pointers and all unused bits

(Register Pointer<7:4>) need to be cleared or set to ‘0’.

each register.

W-0

—

Pointer bits

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

bit 7-4

W: Writable bits

Write ‘0’.

Bits 7-4 must always be cleared or written to ‘0’. This device has additional registers that are reserved

for test and calibration. If these registers are accessed, the device may not perform according to the

specification.

bit 3-0

Pointer bits

0000

= RFU, Reserved for Future Use (Read-Only register)

0001

= Configuration register (CONFIG)

0010

= Alert Temperature Upper Boundary Trip register (TUPPER)

0011

= Alert Temperature Lower Boundary Trip register (TLOWER)

0100

= Critical Temperature Trip register (TCRIT)

0101

= Temperature register (TA)

0110

= Manufacturer ID register

0111

= Device ID/Revision register

1000

= Resolution register

1xxx

= Reserved(1)

Note 1:

Some registers contain calibration codes and should not be accessed.

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