Datasheet

ADE7116/ADE7156/ADE7166/ADE7169/ADE7566/ADE7569
Rev. B | Page 104 of 152
The LCD waveform frequency, f
LCD
, is the frequency at which
the LCD switches the active common line. Thus, the LCD
waveform frequency depends heavily on the multiplex level.
The frame rate and LCD waveform frequency are set by f
LCDCLK
,
the multiplex level, and the FD[3:0] frame rate selection bits in
the LCD clock SFR (LCDCLK, Address 0x96).
The LCD module provides 16 different frame rates for
f
LCDCLK
= 2048 Hz, ranging from 8 Hz to 128 Hz for an LCD
with 4× multiplexing. Fewer options are available with
f
LCDCLK
= 128 Hz, ranging from 8 Hz to 32 Hz for a 4× multi-
plexed LCD. The 128 Hz clock is beneficial for battery
operation because it consumes less power than the 2048 Hz
clock. The frame rate is set by the FD bits in the LCD clock
SFR (LCDCLK, Address 0x96); see Tabl e 93 and Table 9 4.
The LCD waveform is inverted at twice the LCD waveform
frequency, f
LCD
. This way, each frame has an average dc offset
of 0. ADC offset degrades the lifetime and performance of
the LCD.
BLINK MODE
Blink mode is enabled by setting the BLINKEN bit (Bit 5) in the
LCD Configuration SFR (LCDCON, Address 0x95). This mode
is used to alternate between the LCD on state and LCD off state
so that the LCD screen appears to blink. There are two blinking
modes: a software controlled blink mode and an automatic
blink mode.
Software Controlled Blink Mode
The LCD blink rate can be controlled by user code with the
BLKMOD bits in the LCD clock SFR (LCDCLK, Address 0x96)
by toggling the bits to turn the display on and off at a rate
determined by the MCU code.
Automatic Blink Mode
There are five blink rates available if the RTC peripheral is
enabled. These blink rates are selected by the BLKMOD and
BLKFREQ bits in the LCD clock SFR (LCDCLK, Address 0x96);
see Tabl e 92.
DISPLAY ELEMENT CONTROL
A bank of 15 bytes of data memory located in the LCD module
controls the on or off state of each segment of the LCD. The
LCD data memory is stored in Address 0 through Address 14 in
the LCD module. Each byte configures the on and off states of two
segment lines. The LSBs store the state of the even numbered
segment lines, and the MSBs store the state of the odd numbered
segment lines. For example, LCD Data Address 0 refers to
Segment Line 1 and Segment Line 0 (see Table 99). Note that the
LCD data memory is maintained in the PSM2 operating mode.
The LCD data memory is accessed indirectly through the LCD
pointer SFR (LCDPTR, Address 0xAC) and LCD Data SFR
(LCDDAT, Address 0xAE). Moving a value to the LCDPTR SFR
selects the LCD data byte to be accessed and initiates a read or
write operation (see Table 96 ).
Writing to LCD Data Registers
To update the LCD data memory, first set the LSB of the LCD
Configuration Y SFR (LCDCONY, Address 0xB1) to freeze the
data being displayed on the LCD while updating it. This
operation ensures that the data displayed on the screen does not
change while the data is being changed. Then, move the data to
the LCD data SFR (LCDDAT, Address 0xAE) prior to accessing
the LCD pointer SFR (LCDPTR, Address 0xAC). When the
MSB of the LCD pointer SFR (LCDPTR, Address 0xAC) is set,
the content of the LCD data SFR (LCDDAT, Address 0xAE) is
transferred to the internal LCD data memory designated by the
address in the LCDPTR SFR. Clear the LSB of the LCD
Configuration Y SFR (LCDCONY, Address 0xB1) when all of
the data memory has been updated to allow the use of the new
LCD setup for display.
Sample 8052 code to update the segments attached to FP10 and
FP11 pins, use the following sample 8052 code:
ORL LCDCONY,#01h ;start updating the data
MOV LCDDAT,#FFh
MOV LCDPTR,#80h OR 05h
ANL LCDCONY,#0FEh ;update finished
Reading LCD Data Registers
When the MSB of the LCD Pointer SFR (LCDPTR, Address
0xAC) is cleared, the content of the LCD data memory address
designated by LCDPTR is transferred to the LCD data SFR
(LCDDAT, Address 0xAE).
Sample 8052 code to read the contents of LCD Data Memory
Address 0x07, which holds the on and off state of the segments
attached to FP14 and FP15, is as follows.
MOV LCDPTR,#07h
MOV R1, LCDDAT