MCP98244 datasheet(9/52 Pages) MICROCHIP

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DS20002327D-page 9

MCP98244

4.0

SERIAL COMMUNICATION

4.1

2-Wire Standard Mode I2C™

Protocol-Compatible Interface

The MCP98244 serial clock input (SCL) and the

bidirectional serial data line (SDA) form a 2-wire

bidirectional

Standard

mode

I2C-compatible

communication port (refer to the Input/Output Pin DC

Characteristics table and Serial Interface Timing Spec-

ifications table).

The following bus protocol has been defined:

TABLE 4-1:

MCP98244 SERIAL BUS

PROTOCOL DESCRIPTIONS

4.1.1

DATA TRANSFER

Data transfers are initiated by a Start condition

(START), followed by a 7-bit device address and a

read/write bit. An Acknowledge (ACK) from the client

confirms the reception of each byte. Each access must

be terminated by a Stop condition (STOP).

Repeated communication is initiated after tB-FREE.

This device does not support sequential register

read/write. Each register needs to be addressed using

the Register Pointer.

This device supports the Receive Protocol. The

read. Each repeated read or receive begins with a Start

condition and address byte. The MCP98244 retains the

previously selected register. Therefore, they output

data from the previously-specified register (repeated

pointer specification is not necessary).

4.1.2

HOST/CLIENT

The bus is controlled by a host device (typically a

microcontroller) that controls the bus access and

generates the Start and Stop conditions. The

MCP98244 is a client device and does not control other

devices in the bus. Both host and client devices can

operate as either transmitter or receiver. However, the

host device determines which mode is activated.

4.1.3

START/STOP CONDITION

A high-to-low transition of the SDA line (while SCL is

high) is the Start condition. All data transfers must be

preceded by a Start condition from the host. A

low-to-high transition of the SDA line (while SCL is

high) signifies a Stop condition.

If a Start or Stop condition is introduced during data

transmission, the MCP98244 releases the bus. All data

transfers are ended by a Stop condition from the host.

4.1.4

ADDRESS BYTE

Following the Start condition, the host must transmit an

8-bit address byte to the MCP98244. The address for

the

MCP98244

Temperature

Sensor

‘0011,A2,A1,A0’ in binary, where the A2, A1 and A0

bits are set externally by connecting the corresponding

pins to VDD ‘1’ or GND ‘0’. The 7-bit address

transmitted in the serial bit stream must match the

selected address for the MCP98244 to respond with an

ACK. Bit 8 in the address byte is a read/write bit.

Setting this bit to ‘1’ commands a read operation, while

‘0’ commands a write operation (see Figure 4-1).

FIGURE 4-1:

Device Addressing.

4.1.5

DATA VALID

After the Start condition, each bit of data in

transmission needs to be settled for a time specified by

tSU-DATA before SCL toggles from low-to-high (see

Serial Interface Timing Specifications table).

Term

Description

Host

The device that controls the serial bus,

typically a microcontroller.

Client

The device addressed by the host,

such as the MCP98244.

Transmitter Device sending data to the bus.

Receiver

Device receiving data from the bus.

START

A unique signal from host to initiate

serial interface with a client.

STOP

A unique signal from the host to

terminate serial interface from a client.

Read/Write A read or write to the MCP98244

registers.

ACK

A receiver Acknowledges (ACK) the

reception of each byte by polling the

bus.

NAK

A receiver Not-Acknowledges (NAK) or

releases the bus to show End-of-Data

(EOD).

Busy

Communication is not possible

because the bus is in use.

Not Busy

The bus is in the idle state, both SDA

and SCL remain high.

Data Valid

SDA must remain stable before SCL

becomes high in order for a data bit to

be considered valid. During normal

data transfers, SDA only changes state

while SCL is low.

1 2 34 5 678 9

SCL

SDA

0 0

1 1 A2 A1 A0

Start

Address Byte

Client

Address

R/W

MCP98244 Response

Code

Address

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