ez80f91 ZiLOG Semiconductor, ez80f91 Datasheet - Page 223

• Manufacturer Part Number: ez80f91
• Description: Ez80 Acclaimplus!? Connectivity Assp Ez80f91 Assp
• Manufacturer: ZiLOG Semiconductor

eZ80F91 ASSP
Product Specification
215
Transferring Data
Byte Format
Every character transferred on the SDA line must be a single 8-bit byte. The number of
bytes that is transmitted per transfer is unrestricted. Each byte must be followed by an
Acknowledge (ACK). Data is transferred with the most-significant bit (msb) first.
Figure 45
illustrates a receiver that holds the SCL line Low to force the transmitter into a
Wait state. Data transfer then continues when the receiver is ready for another byte of data
and releases SCL.
SDA Signal
MSB
Acknowledge from
Acknowledge from
Receiver
Receiver
SCL Signal
1
2
8
9
1
9
S
P
ACK
START Condition
STOP Condition
Clock Line Held Low By Receiver
2
Figure 45. I
C Frame Structure
Acknowledge
Data transfer with an ACK function is obligatory. The ACK-related clock pulse is gen-
erated by the master. The transmitter releases the SDA line (High) during the ACK
clock pulse. The receiver must pull down the SDA line during the ACK clock pulse so
that it remains stable (Low) during the High period of this clock pulse. See
Figure 46
on page 216.
A receiver that is addressed is obliged to generate an ACK after each byte is received.
When a slave receiver does not acknowledge the slave address (for example, unable to
receive because it is performing some real-time function), the data line must be left High
by the slave. The master then generates a STOP condition to abort the transfer.
If a slave receiver acknowledges the slave address, but cannot receive any more data
bytes, the master must abort the transfer. The abort is indicated by the slave generating the
Not Acknowledge (NACK) on the first byte to follow. The slave leaves the data line High
and the master generates the STOP condition.
If a master receiver is involved in a transfer, it must signal the end of the data stream to the
slave transmitter by not generating an ACK on the final byte that is clocked out of the
slave. The slave transmitter must release the data line to allow the master to generate a
STOP or a repeated START condition.
2
PS027001-0707
I
C Serial I/O Interface