X9448-2.7 XICOR [Xicor Inc.], X9448-2.7 Datasheet - Page 8

• Manufacturer Part Number: X9448-2.7
• Description: Mixed Signal with 2-Wire Interface
• Manufacturer: XICOR [Xicor Inc.]

X9448
Increment/Decrement Wiper Counter Register
Enable Increment/decrement of the WCR pointed to by P
REGISTERS OPERATION
Both XDCP potentiometers and voltage comparators
share the serial interface and share a common archi-
tecture. Each potentiometer and voltage comparator is
associated with wiper counter and analog control reg-
isters and eight data registers. A detailed discussion of
the register organization and array operation follows.
Wiper Counter (WCR) and Analog Control
Registers (ACR)
The X9448 contains two wiper counter registers one
for each XDCP potentiometer and two analog control
registers, one for each of the two voltage comparators.
The wiper counter register is equivalent to a serial-in,
parallel-out counter with its outputs decoded to select
one of sixty-four switches along its resistor array. The
contents of the wiper counter register and analog con-
trol register can be altered in four ways: it may be writ-
ten directly by the host via the Write WCR instruction
(serial load); it may be written indirectly by transferring
the contents of one of four associated data registers
(DR) via the XFR data register instruction (parallel
load); it can be modified one step at a time by the
increment/decrement instruction (WCR only). Finally, it
is loaded with the contents of its data register zero (R0)
upon power-up.
The wiper counter and analog control register are vola-
tile registers; that is, their contents are lost when the
X9448 is powered-down. Although the registers are
automatically loaded with the value in R0 upon power-
up, it should be noted this may be different from the
value present at power-down.
Programming the ACR is similar to the WCR. However,
the 6 bits in the WCR positions the wiper in the resistor
array while 3 bits in the ACR control the comparator
and its output.
REV 1.0 6/21/00
S
A
R
T
T
0 1 0 1
device type
identifier
A
3
addresses
device
A
2
A
1
A
0
S
A
C
K
0 0 1 0 0 0
instruction
opcode
addresses
www.xicor.com
WCR
P
1
1
-P
P
0
0
.
Data Registers (DR)
Each potentiometer and each voltage comparator has
four nonvolatile data registers (DR). These can be read
or written directly by the host and data can be trans-
ferred between any of the four data registers and the
WCR or ACR. It should be noted all operations chang-
ing data in one of these registers is a nonvolatile oper-
ation and will take a maximum of 10ms.
If the application does not require storage of multiple
settings for the potentiometer or comparator, these reg-
isters can be used as regular memory locations that
could store system parameters or user preference data.
REGISTER DESCRIPTIONS
Wiper Counter Register (WCR)
WP0-WP5 identify wiper position.
Analog Control Register (ACR)
Shutdown
“1”
“0”
Enable
“1”
“0”
C
S
A
K
0
0
D
I/
(sent by master on SDA)
0
increment/decrement
D
I/
indicates power is connected to the voltage
comparator.
indicates power is not connected to the voltage
comparator.
indicates the output buffer of the voltage com-
parator is enabled.
indicates the output buffer of the voltage com-
parator is disabled.
0
User
-bit5
.
WP5 WP4 WP3 WP2 WP1
P1 P0: 00 or 01 only.
(volatile)
.
User
-bit4
.
Characteristics subject to change without notice.
(volatile)
.
User
-bit3 Latch Enable
D
I/
D
I/
O
S
P
T
(LSB)
WP0
Shut-
down
(LSB)
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