X9455 Datasheet, PDF (13/18 Pages) Intersil Corporation – Dual Two-wiper Digitally-Controlled (XDCP) Potentiometer

X9455
Signals from
the Master
Signal at SDA
Signals from
the Slave
If bit 0 of data byte = 1,
DR contents move to WCR
during this ACK period
S
t
a
Slave
r
Address
t
Status Register
Address
S
DR select
t
Data
o
p
0101
0 00000111
00000x x1
A
A
A
C
C
C
K
K
K
FIGURE 6. STATUS REGISTER WRITE (USES STANDARD BYTE WRITE SEQUENCE TO SET UP ACCESS TO A DATA REGISTER)
TABLE 4. ADDRESSING FOR 2-WIRE INTERFACE ADDRESS
BYTE
ADDRESS (HEX)
CONTENTS
0
Wiper 0A
1
Wiper 1B
2
Wiper 1A
3
Wiper 0B
4
Not Used
5
Not Used
6
Not Used
7
Status Register
All other address bits in the address byte must be set to “0”
during 2-wire write operations and their value should be
ignored when read.
Byte Write Operation
For any Byte Write operation, the X9455 requires the Slave
Address byte, an Address Byte, and a Data Byte (See Figure
7). After each of them, the X9455 responds with an ACK.
The master then terminates the transfer by generating a
STOP condition. At this time, if the write operation is to a
volatile register (WCR, or SR), the X9455 is ready for the
next read or write operation. If the write operation is to a
nonvolatile register (DR), and the WP pin is high, the X9455
begins the internal write cycle to the nonvolatile memory.
During the internal nonvolatile write cycle, the X9455 does
not respond to any requests from the master. The SDA
output is at high impedance.
The SR bits and WP pin determine the register being
accessed through the 2-wire interface. See Table 2 on page
9.
As noted before, any write operation to a Data Register
(DR), also transfers the contents of all the data registers in
that row to their corresponding WCR.
For example, to write 3Ahex to the Level 1 Data Register of
wiper 1A (DR1A1) the following sequence is required:
START
Slave Address
ACK
0101 0000
(Hardware Address = 000,
and a Write command)
Address Byte
ACK
0000 0111
(Indicates Status Register
address)
Data Byte
ACK
0000 0011 (Data Register Level 1 and
NVEnable selected)
(note: at this ACK, the WCRs are all updated with their
respective DR.)
STOP
START
Slave Address
ACK
Address Byte
ACK
Data Byte
ACK
STOP
0101 0000
0000 0010
0011 1010
(Hardware address = 000,
Write command)
(Access Wiper 1A)
(Write Data Byte 3Ah)
During the sequence of this example, WP pin must be high,
and A0, A1, and A2 pins must be low. When completed, the
DR1A1 register and the WCR1A of Wiper 1A will be set to
3Ah, and the other data registers in Row 1 will transfer their
contents to the respective WCRs.
13
FN8202.0
November 10, 2004