X9241
Cascade Mode
The X9241 provides a mechanism for cascading the
arrays. That is, the sixty-three resistor elements of one
array may be cascaded (linked) with the resistor ele-
ments of an adjacent array.
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).
The state of CM enables or disables (normal operation)
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
Figure 9. Cascading Arrays
VL0
VH0
VW0
POT 1
WCR1
VL1
VH1
VW1
POT 2
WCR2
VL2
VH2
VW2
POT 3
WCR3
= EXTERNAL
CONNECTION
VL3
VH3
VW3
DW bit of the WCR is set to “0” the wiper is enabled;
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 VH, VL 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 deter-
mined 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, a global XFR WCR to Data
Register command must be issued before power-down.
POT 0
WCR0
3864 ILL F16.1
8
XICOR [ XICOR INC. ]
