X9241A
Cascade Mode
The X9241A provides a mechanism for cascading the
arrays. That is, the sixty-three resistor elements of one array
may be cascaded (linked) with the resistor elements of an
adjacent array. The V
L
/R
L
of the higher order array must be
connected to the V
H
/R
H
of the lower order array (See
Figure 9).
when set to “1” the wiper is disabled. If the wiper is disabled,
the wiper terminal will be electrically isolated and float.
When operating in cascade mode V
H
/R
H
, V
L
/R
L
and the
wiper terminals of the cascaded arrays must be electrically
connected externally. All but one of the wipers must be
disabled. The user can alter the wiper position by writing
directly to the WCR or indirectly by transferring the contents
of the Data Registers to the WCR or by using the
Increment/Decrement command.
When using the Increment/Decrement command the wiper
position will automatically transition between arrays. The
current position of the wiper can be determined by reading
the WCR registers; if the DW bit is “0”, the wiper in that array
is active. If the current wiper position is to be maintained on
power-down a global XFR WCR to Data Register command
must be issued to store the position in NV memory before
power-down.
It is possible to connect three or all four potentiometers in
cascade mode. It is also possible to connect POT 3 to POT 0
as a cascade. The requirements for external connections of
V
L
/R
L
, V
H
/R
H
and the wipers are the same in these cases.
Cascade Control Bits
The data byte, for the three-byte commands, contains 6 bits
(LSBs) for defining the wiper position plus two high order
bits, CM (Cascade Mode) and DW (Disable Wiper, normal
operation).
The state of the CM bit (bit 7 of WCR) enables or disables
cascade mode. When the CM bit of the WCR is set to “0” the
potentiometer is in the normal operation mode. When the
CM bit of the WCR is set to “1” the potentiometer is
cascaded with its adjacent higher order potentiometer. For
example; if bit 7 of WCR2 is set to “1”, pot 2 will be cascaded
to pot 3.
The state of DW enables or disables the wiper. When the
DW bit (bit 6 of the WCR) is set to “0” the wiper is enabled;
Pot 0
WCR0
V
L0
/R
L0
V
H0
/R
H0
V
W0
/R
W0
Pot 1
WCR1
V
L1
/R
L1
V
H1
/R
H1
V
W1
/R
W1
Pot 2
WCR2
V
L2
/R
L2
V
H2
/R
H2
V
W2
/R
W2
Pot 3
External
Connection
WCR3
V
L3
/R
L3
V
H3
/R
H3
V
W3
/R
W3
=
FIGURE 9. CASCADING ARRAYS
9
FN8164.5
December 14, 2006
INTERSIL [ INTERSIL CORPORATION ]
