MCP3421 datasheet(23/42 Pages) MICROCHIP

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DS22003E-page 23

MCP3421

5.6.5

ACKNOWLEDGE AND NON-

ACKNOWLEDGE

The Master (microcontroller) and the slave (MCP3421)

use an acknowledge pulse as a hand shake of commu-

nication for each byte. The ninth clock pulse of each

byte is used for the acknowledgement. The clock pulse

is always provided by the Master (microcontroller) and

the acknowledgement is issued by the receiving device

of the byte (Note: The transmitting device must release

the SDA line during the acknowledge pulse.). The

acknowledgement is achieved by pulling-down the

SDA line “LOW” during the 9th clock pulse by the

receiving device.

During

reads,

the

Master

(microcontroller)

can

terminate the current read operation by not providing

an acknowledge bit (not Acknowledge (NAK)) on the

last byte. In this case, the MCP3421 device releases

the SDA line to allow the Master (microcontroller) to

generate a STOP or repeated START condition.

The

non-acknowledgement

(NAK)

issued

providing the SDA line to “HIGH” during the 9th clock

pulse.

FIGURE 5-6:

Data Transfer Sequence on I2C Serial Bus.

SCL

SDA

(A)

(B)

(D)

(A)

(C)

START

CONDITION

ADDRESS OR

ACKNOWLEDGE

VALID

DATA

ALLOWED

TO CHANGE

STOP

CONDITION

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