CAT5132GZ-100TE13 CATALYST [Catalyst Semiconductor], CAT5132GZ-100TE13 Datasheet - Page 8

• Manufacturer Part Number: CAT5132GZ-100TE13
• Description: 15 Volt Digitally Programmable Potentiometer (DPP) with 128 Taps and 2-wire Interface
• Manufacturer: CATALYST [Catalyst Semiconductor]

Doc. No. 25092, Rev. 00
CAT5132
DEVICE DESCRIPTION
Access Control Register
The volatile register WCR and the non-volatile register
DR of CAT5132 are accessed only by addressing the
volatile Access Register AR first, using the 3 byte I
interface for all read and write operations (see Table 1).
The first byte is the slave address/instruction byte (see
details below). The second byte contains the address
(02h) of the AR register. The data in the third byte
controls which register WCR (80h) or DR (00h) is being
addressed (see Figure 5).
Slave Address Instruction Byte Description
The first byte sent to the CAT5132 from the master
processor is called the Slave/DPP Address Byte. The
most significant five bits of the slave address are a
device type identifier. These bits for the CAT5132 are
fixed at 01010 (refer to Table 2).
Table 1. Access Control Register
Table 2. Byte 1 Slave Address and Instruction Byte
S
S
T
T
(
M
D I
0
0
0
S
4
) B
1
1
0
0
1st byte
BUS ACTIVITY:
1
1
D I
1
3
0
0
SDA LINE
MASTER
Figure 5. Access Register Addressing Using 3 Bytes
0
0
D
0
0
e
v
D I
c i
0
0
0
S
A
R
T
T
S
2
e
T
& INSTRUCTION
A
A
y
FIXED
p
ADDRESS
e
0
0
SLAVE
d I
VARIABLE
e
0
0
D I
n
1
i f i t
1
A
0
0
2
R
r e
C
2nd byte
a
A
C
K
0
0
d
d
e r
8
s s
0
0
AR REGISTER
The next two bits, A1 and A0, are the internal slave
address and must match the physical device address
which is defined by the state of the A1 and A0 input pins
to successfully address the CAT5132. Only the device
with slave address matching the input byte will be
accessed by the master. This allows up to 4 devices to
reside on the same bus. The A1 and A0 inputs can be
actively driven by CMOS input signals or tied to V
Ground.
The last bit is the READ/WRITE bit and determines the
function to be performed. If it is a “1” a read command is
initiated and if it is a “0” a write is initiated. For the AR
register only write is allowed.
After the Master sends a START condition and the slave
address byte, the CAT5132 monitors the bus and
responds with an acknowledge (on the SDA line) when
its address matches the transmitted slave address.
-
D I
ADDRESS
0
0
2
0
0
0
h
1
1
0
0
C
A
K
A
A
S
A
X
SELECTION
a l
1
WCR/DR
0
1
v
WC
e
0
0
A
R
d
8 (
d
0
0
0
e r
h
/ )
A
s s
3rd byte
X
0
0
Characteristics subject to change without notice
D
0
C
A
K
R
P
S
O
P
T
0 (
0
0
0
© 2005 by Catalyst Semiconductor, Inc.
) h
s
0
0
e
R
e l
e
i t c
0
0
a
L (
/ R W
on
/ d
X
S
0
0
W
) B
i r
A
A
e t
SP
S
P
CC
or