f
=
Blink
f
ACLK/VLO
(LCDB 1) × 2
9+LCDBLKPREx
LCD_C Operation
936
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
LCD_C Controller
With LCDPREx = 001 and LCDDIVx = 11011:
f
LCD
= 32768 Hz / ((27+1) × 2
1
) = 32768 Hz / 56 = 585 Hz
The lowest frequency has the lowest current consumption. The highest frequency has the least flicker.
36.2.3 Blanking the LCD
The LCD controller allows blanking the complete LCD. The LCDSON bit is combined with a logical AND
with each segment's memory bit. When LCDSON = 1, each segment is on or off according to its bit value.
When LCDSON = 0, each LCD segment is off.
36.2.4 LCD Blinking
The LCD controller also supports blinking. In static and 2-mux to 4-mux mode, the blinking mode
LCDBLKMODx = 01 allows blinking of individual segments; with LCDBLKMODx = 10 all segments are
blinking; and with LCDBLKMODx = 00 blinking is disabled. In 5-mux mode and above, only blinking mode
LCDBLKMODx = 10 that allows blinking of all segments is available; if another mode is selected, blinking
is disabled.
36.2.4.1 Blinking Memory
In static and 2-mux to 4-mux mode, a separate blinking memory is implemented to select the blinking
segments. To enable individual segments for blinking, the corresponding bit in the blinking memory
LCDBMx registers must be set. The memory uses the same structure as the LCD memory (see
). Each memory bit corresponds to one LCD segment or is not used, depending on the multiplexing
mode LCDMXx. To enable blinking for a LCD segment, its corresponding memory bit is set.
The blinking memory can also be accessed word-wise using the even addresses starting at LCDBM1,
LCDBM3, ...
Setting the bit LCDCLRBM clears all blinking memory registers at the next frame boundary. It is
automatically reset after the registers are cleared.
36.2.4.2 Blinking Frequency
The blinking frequency f
BLINK
is selected with the LCDBLKPREx and LCDBLKDIVx bits. The same clock is
used as selected for the LCD frequency f
LCD
. The resulting f
BLINK
frequency is calculated by:
The divider generating the blinking frequency f
BLINK
is reset when LCDBLKMODx = 00. After a blinking
mode LCDBLKMODx = 01 or 10 is selected, the enabled segments or all segments go blank at the next
frame boundary and stay off for half of a BLKCLK period. Then they go active at the next frame boundary
and stay on for another half BLKCLK period before they go blank again at a frame boundary.
NOTE:
Blinking Frequency Restrictions
The blinking frequency must be smaller than the frame frequency f
Frame
.
The blinking frequency should only be changed when LCDBLKMODx = 00.
36.2.4.3 Dual Display Memory
In static and 2-mux to 4-mux mode, the blinking memory can also be used as a secondary display
memory when no blinking mode LCDBLKMODx = 01 or 10 is selected. The memory to be displayed can
be selected either manually using the LCDDISP bit or automatically with LCDBLKMODx = 11.
With LCDDISP = 0, the LCD memory is selected, and with LCDDISP = 1 the blinking memory is selected
as display memory. Switching between the memories is synchronized to the frame boundaries.