
REV. 0
AD9886
–29–
Data is read from the control registers of the AD9886 in a similar
manner. Reading requires two data transfer operations:
The base address must be written with the R/
W
bit of the slave
address byte LOW to set up a sequential read operation.
Reading (the R/
W
bit of the slave address byte HIGH) begins at
the previously established base address. The address of the read
register autoincrements after each byte is transferred.
To terminate a read/write sequence to the AD9886, a stop sig-
nal must be sent. A stop signal comprises a LOW-to-HIGH
transition of SDA while SCL is HIGH.
A repeated start signal occurs when the master device driving
the serial interface generates a start signal without first generat-
ing a stop signal to terminate the current communication. This
is used to change the mode of communication (read, write)
between the slave and master without releasing the serial inter-
face lines.
Serial Interface Read/Write Examples
Write to one control register
Start signal
Slave Address byte (R/
W
bit = LOW)
Base Address byte
Data byte to base address
Stop signal
Write to four consecutive control registers
Start signal
Slave Address byte (R/
W
bit = LOW)
Base Address byte
Data byte to base address
Data byte to (base address + 1)
Data byte to (base address + 2)
Data byte to (base address + 3)
Stop signal
Read from one control register
Start signal
Slave Address byte (R/
W
bit = LOW)
Base Address byte
Start signal
Slave Address byte (R/
W
bit = HIGH)
Data byte from base address
Stop signal
Read from four consecutive control registers
Start signal
Slave Address byte (R/
W
bit = LOW)
Base Address byte
Start signal
Slave Address byte (R/
W
bit = HIGH)
Data byte from base address
Data byte from (base address + 1)
Data byte from (base address + 2)
Data byte from (base address + 3)
Stop signal
BIT 7
SDA
SCL
ACK
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Figure 28. Serial Interface—Typical Byte Transfer
SDA
SCL
t
BUFF
t
STAH
t
DHO
t
DSU
t
DAL
t
DAH
t
STASU
t
STOSU
Figure 27. Serial Port Read/
Write
Timing