MCP9843 datasheet(40/62 Pages) MICROCHIP

40 / 62 page

MCP9843/98243

DS22153C-page 40

5.3.4

READ OPERATION

Read operations are initiated in the same way as write

operations, with the exception that the R/W bit of the

slave address is set to ‘1’. There are three basic types

of read operations: current address read, random read

and sequential read.

5.3.4.1

Current Address Read

The MCP98243 contains an address counter that

maintains the address of the last word accessed,

internally incremented by ‘1’. Therefore, if the previous

access (either a read or write operation) was to

address n, the next current address read operation

would access data from address n+1. Upon receipt of

the slave address with R/W bit set to ‘1’, the MCP98243

issues an acknowledge and transmits the 8-bit data

word. The master will not acknowledge (NAK) the

transfer but does generate a Stop condition and the

MCP98243 discontinues transmission (Figure 5-18).

FIGURE 5-18:

Reading Current Word Address (See Section 4.0 “Serial Communication”).

TABLE 5-5:

DEVICE RESPONSE WHEN READING SWP/CWP/PWP (NOTE)

Status

Command

ACK

Address

ACK

Data Byte

ACK

Not Protected

SWP/CWP/PWP

ACK

NoACK

Protected with SWP

SWP

NoACK

CWP

ACK

NoACK

PWP

ACK

NoACK

Permanently Protected

SWP/CWP/PWP

NoACK

Note:

X is defined as ‘don’t care’.

567

Address Byte

Current Word Address

MCP98243

Master

SDA

SCL

Note:

In this example, the current word address is the

previously accessed address location n plus 1.

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