MCP9844 datasheet(12/44 Pages) MICROCHIP

12 / 44 page

MCP9844

DS20005192A-page 12

 2013 Microchip Technology Inc.

5.1

Registers

The MCP9844 device has several registers that are

user accessible. These registers include the Capability

Upper-Boundary and Lower-Boundary Trip registers,

Critical

Temperature

Trip

Temperature

Device Identification register.

The Temperature register is read-only and is used to

access the ambient temperature data. The data is

loaded in parallel to this register after tCONV. The Event

Temperature Upper-Boundary and Lower-Boundary

Trip registers are read/writes. If the ambient

temperature drifts beyond the user-specified limits, the

MCP9844 device outputs a signal using the Event pin

(refer

Section 5.2.3

“Event

Output

Configuration”

). In addition, the Critical Temperature

Trip register is used to provide an additional critical

temperature limit.

The Capability register is used to provide bits

describing the MCP9844’s capability in measurement

resolution, measurement range and device accuracy.

The device Configuration register provides access to

configure the MCP9844’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 MCP9844 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

(bits 7-4) need to be cleared or set to ‘0’. Register 5-1

describes the pointer or the address of 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

Writable Bits:

Write ‘0’

bit 3-0

Pointer Bits:

0000

Capability register

0001

Configuration register (CONFIG)

0010

Event Temperature Upper-Boundary Trip register (TUPPER)

0011

Event 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

Reserved

1001

Resolution register

1XXX

Reserved (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.)

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