Rainbow Electronics ISD5216 - Manual (Page 70)

I5216 SERIES
Advanced Information
PRELIMINARY
Publication Release Date: November 30, 2001
- 70 Revision A1
SYSTEM CONFIGURATION
A device generating a message is a ‘transmitter’; a device receiving a message is the ‘receiver’. The
device that controls the message is the ‘master’ and the devices that are controlled by the master are
the ‘slaves’.
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 bit. The acknowledge bit is
a HIGH level signal put on the interface 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. In addition, 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.
MBC645
SDA
SCL
MICRO -
CONTROLLER STATIC
RAM OR
EEPROM LCD
DRIVER
GATE
ARRAY
ISD 5116
Example of an I C-bus configuration using two microcontrollers
2
Acknowledge on the I 2 C-bus
MBC602
S
START
condition
9 8 2 1
clock pulse for
acknowledgement
not acknowledge
acknowledge
DATA OUTPUT
BY TRANSMITTER
DATA OUTPUT
BY RECEIVER
SCL FROM
MASTER
Data output by
transmitter
Data output by
receiver
SCL from Master
Not acknowlwedge
Not acknowlwedge
Clock pulse for
acknowledgement
Start condition
Acknowledge on the I
2
C-bus
7 2 8 9