PCA88021 datasheet(11/34 Pages) NXP

11 / 34 page

PCA8802_1

Product data sheet

Rev. 01 — 19 February 2009

11 of 34

NXP Semiconductors

PCA8802

Smartcard RTC

9.5.6 Acknowledge

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

transmitter to receiver is unlimited, but the duration of the access must not exceed

32 seconds. Each byte of eight bits is followed by an acknowledge bit. The acknowledge

bit is a HIGH level signal put on the bus by the transmitter during which time the master

generates an extra acknowledge related clock pulse. 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 is shown in Figure 16.

9.5.7 Data transfer

Fig 16. Acknowledgement 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

Fig 17. A complete data transfer

001aaj201

1 to 7

ADDRESS

ACK

DATA

START

condition

SCL

SDA

1 to 7

STOP

condition

ACK

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