PCF8564A datasheet(22/44 Pages) NXP

22 / 44 page

PCF8564A_1

Product data sheet

Rev. 1 — 8 October 2009

22 of 44

NXP Semiconductors

PCF8564A

Real time clock and calendar

9.4 Acknowledge

The number of data bytes transferred between the START and STOP conditions from

transmitter to receiver is unlimited. Each byte of eight bits is followed by an acknowledge

cycle.

• A slave receiver, which is addressed, must generate an acknowledge after the

reception of each byte.

• Also a master receiver must generate an acknowledge after the reception of each

byte that has been clocked out of the slave transmitter.

• The device that acknowledges must pull-down the SDA line during the acknowledge

clock pulse, so that the SDA line is stable LOW during the HIGH period of the

acknowledge related clock pulse (set-up and hold times must be taken into

consideration).

• A master receiver must signal an end of data to the transmitter by not generating an

acknowledge on the last byte that has been clocked out of the slave. In this event the

transmitter must leave the data line HIGH to enable the master to generate a STOP

condition.

Acknowledgement on the I2C-bus is shown in Figure 15.

Fig 14. System conﬁguration

mba605

MASTER

TRANSMITTER /

RECEIVER

SLAVE

RECEIVER

SLAVE

TRANSMITTER /

RECEIVER

MASTER

TRANSMITTER

MASTER

TRANSMITTER /

RECEIVER

SDA

SCL

Fig 15. Acknowledgment on the I2C-bus

mbc602

START

condition

clock pulse for

acknowledgement

not acknowledge

acknowledge

data output

by transmitter

data output

by receiver

SCL from

master

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