X9455 Datasheet, PDF (15/18 Pages) Intersil Corporation – Dual Two-wiper Digitally-Controlled (XDCP) Potentiometer

X9455
Move/Read Operation
The Move/Read operation simultaneously reads the
contents of a data register and moves the contents into the
corresponding DCP’s WCR and all wipers will have their
WCR’s updated with the data register values from the row
that was read. Move/Read operation consists of a one byte,
or three byte instruction followed by one or more Data Bytes
(See Figure 10). To read an arbitrary byte, the master
initiates the operation issuing the following sequence: a
START, the Slave Address byte with the R/W bit set to “0”,
an Address Byte, a second START, and a second Slave
Address byte with the R/W bit set to “1”. After each of the
three bytes, the X9455 responds with an ACK. Then the
X9455 transmits Data Bytes as long as the master responds
with an ACK during the SCL cycle following the eighth bit of
each byte. The master terminates the Move/Read operation
(issuing a STOP condition) following the last bit of the last
Data Byte.
The first byte being read is determined by the current wiper
address and by the Status Register bits, according to Table 1
on page 11. If more than one byte is read, the WCR address
is incremented by one after each byte, in the same way as
during a Page Write operation. After reaching WCR0B, the
WCR address “rolls over” to WCR0A.
On power up, the Address pointer is set to the Data Register
0 of WCR0A.
S
Slave
Signals
t
Address with
from the a
R/W=0
Master
r
t
Signal at SDA
01 01
Signals from the
Slave
0
A
C
K
Address
Byte
S
Slave
t _{Address with}
a
R/W=1
r
t
One or more Data Bytes
S
A
A
C
C
K
K
t
o
p
01 01
A
C
K
1
A
C
K ^{First Read Data}
Byte
Last Read Data
Byte
Setting the Current Address
Current Address Read
Random Address Read
FIGURE 10. MOVE/READ SEQUENCE
15
FN8202.0
November 10, 2004