SMS47
PreliminaryInformation
2
I C PROGRAMMING INFORMATION (CONTINUED)
READ OPERATIONS
Write Cycle
In Progress
Read operations are initiated with the R/W bit of the
identification field set to 1. There are two different Read
options: 1. Current Address Byte Read, and 2. Random
Address Byte Read.
Issue Start
Issue Stop
RandomAddressRead
Issue Slave
Address and
R/W = 0
Random address Read operations allow the Master to
access any register location in a random fashion. This
operation involves a two-step process. First, the Master
issuesawritecommandwhichincludesthestartcondition
and the Slave address field (with the R/W bit set to Write),
followed by the address of the word it is to Read. This
proceduresetstheinternaladdresscounteroftheSMS47
to the desired address. After the word address acknowl-
edge is received by the Master it immediately reissues a
Start condition, followed by another Slave address field
withtheR/WbitsettoREAD. TheSMS47willrespondwith
anAcknowledgeandthentransmitthe8databitsstoredat
the addressed location. At this point the Master sets the
SDA line to NACK and generates a Stop condition. The
SMS47 discontinues data transmission and reverts to its
standbypowermode.
No
ACK
Returned
Yes
Next
Operation
a Write?
No
Yes
Issue Stop
Issue
Address
Proceed
With
Write
Await
Next
Command
Figure 12. Write Flow Chart
S
S
T
O
P
T
Writing Configuration Registers
A
Master
R
T
R
/
W
B B
A A
D D D D D D D D
C C C C C C C C
SDA
X
0 1
1 0
7
6 5 4 3 2 1 0
7
6
5
4
3
2
1
0
2
1
A
C
K
A
C
K
A
C
K
Slave
S
T
A
R
T
S
T
A
R
T
N
A
C
K
S
T
O
P
A
C
K
Reading the Configuration Register
Master
SDA
B B
A A
R
B B
A A
R
/
W
D D D D D D D D
C C C C C C C C
X
/
X
0 1
1 0
0 1
1 0
7
6 5 4 3 2 1 0
7
6 5 4 3 2 1 0
2
1
W
2
1
A
C
K
A
C
K
Slave
Figure 11. Read and Write Operations
SUMMIT MICROELECTRONICS, Inc.
2087 1.0 04/11/05
15
SUMMIT [ SUMMIT MICROELECTRONICS, INC. ]
