AN204779
F²MC-16FX Family, LC-Display
This application note gives a rough overview about how this kind of display works and illuminates some different
methods to control a Liquid Crystal Display (LCD) by a microcontroller.
Contents
1
2
Introduction ...............................................................1
Introduction in Liquid Crystals...................................1
2.1
The Physics .....................................................1
2.2
Addressing .......................................................3
3
Controlling of Liquid Crystals ....................................6
3.1
MB963xx Microcontrollers with
LCD Controller/Driver ......................................6
3.2
External LCD Controller/Driver ...................... 10
3.3
Alphanumeric LCD Module ............................ 11
1
4
LCD Examples ....................................................... 14
4.1
Interfacing MB9638x to LCD Glass DE133.... 14
4.2
Interfacing MB963xx to LCD
Module HD44780 ........................................... 15
5
Conclusion.............................................................. 21
6
Additional Information ............................................. 21
7
Document History ................................................... 22
Introduction
Segment displays based on liquid crystal material are very common if only a small number of characters or symbols
should be displayed.
This application note gives a rough overview about how this kind of display works and illuminates some different
methods to control a Liquid Crystal Display (LCD) by a microcontroller.
Further, the connection to LCD glass and also to alphanumeric LCD modules (with integrated segment and LCD
controller) will be discussed.
2
Introduction in Liquid Crystals
This chapter reflects the technical background of passive LC-segments
2.1
The Physics
The main characteristic of Liquid Crystal is based on anisotropic material. Most common are Nematic LC molecules
all tend to align in the same direction to each other.
In the following, the basic construction and basic function of a standard display will be explained. A first special glass
will polarize random ambient light. When entering the next layer the twisted structure of the crystal-molecules rotates
the polarization of linearly polarized incident light by 90 degrees, so that it passes through a second polarizer, and the
device appears white.
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F²MC-16FX Family, LC-Display
Figure 1.LC Display Polarized with Ambient Light
H-Polarized light
Randomly
Polarized
Light
LinearPolarizer
Crystal-molecules
Glass with
Electrode
(Segment)
V-Polarized light
Glass with
Electrode
(COM-plane)
Analyzer
(2nd Polarizer)
If an electric field is applied to the cell, the molecular axes align with the field and the structure no longer twists the
polarization of the incident light, so the emerging light is absorbed by the second polarizer and the device appears
black.
If the field is removed the Nematic relaxes to the twisted structure.
The mobility of the crystal depends very much on the temperature; in cold environment the movement is very slow.
Seen from the electrical side one element can be compared with a capacitor, together with the signal-lines it can be
handled as a RC-element.
Direct current will attack Liquid crystals and last destroy it. So any DC-offset should be prevented from the molecules.
In general, datasheets of LC-displays allow less than 50mV.
Figure 2. LC Display with Electric Field Applied
Polarized light
Randomly
Polarized
Light
LinearPolarizer
Crystal-molecules
Glass with
Electrode
(Segment)
Glass with
Electrode
(COM-plane)
Analyzer
(2nd Polarizer)
~
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F²MC-16FX Family, LC-Display
2.2
Addressing
Addressing is the process to turn on and off a pixel in order to create an image. There are two main types of
addressing, direct and multiplexing.
2.2.1
Static addressing
Direct addressing is convenient for displays with only a few elements that have to be activated. With direct
addressing, each pixel in the display has its own drive circuit. The control-voltage has to be applied to each element.
Figure 3. 7-Segment Display using Static Addressing
COM
a
b
f
g
c
e
d
Segment-lines
A common application of direct addressing is the traditional seven-segment liquid crystal display, found in
wristwatches and similar devices.
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F²MC-16FX Family, LC-Display
2.2.2
Multiplexed addressing
In multiplex addressing, a larger number of pixels are involved. When the elements are in a regular order, they can be
addressed by their row and column instead of each element being driven separately.
Figure 4. Multiplexed Addressing
row1
row2
row3
row4
col1
col2
col3
col4
This reduces the complexity of the circuitry because each pixel no longer needs its own driver circuit. If you have a
4x4 matrix of pixels, with direct addressing, you need 16 individual drivers. However, if you use multiplex addressing,
you only need eight drivers, one for each row and one for each column.
Figure 5. 7-Segment Display using Multiplexed Addressing
f
f
b
c
d
SEG3
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b
COM2
c
COM3
g
g
e
COM1
a
a
e
dp
SEG2
d
SEG1
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dp
COM4
SEG0
4
F²MC-16FX Family, LC-Display
Figure 6. Output Waveform (1/2 duty cycle, 1/3 Bias)
Example:
Figure 6 at the right represents the 3x2
format (bias 1:3, duty 1:2).
Only two COM-lines (duty 1:2) are used
and three output-voltages V1, V2 and
V3 (bias 1:3) will be output.
The shown waveform demonstrates two
segments:
SEG2n=OFF
and
SEG2n+1=ON.
The algebraically summed voltages
between the COM- and the segmentlines are depicted in the last 4
waveforms.
In order to prevent deterioration of the
crystals by DC power the LCD is driven
with a two-frame AC waveform.
Voltage levels:
V0 = 0V , V1= Vcc/3
V2 = 2Vcc/3, V3 = Vcc
(1 ) (V3 – V1) = - (V0 – V1)
(2) V1 = V3/3
(3) V2 =2V3/3
In addition, the time-interval each signal
is applied has to be constant, too.
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F²MC-16FX Family, LC-Display
If the number of common planes (COMx) is increased, the time each pixel is controlled (duty cycle) decrease what
result in worse contrast and angle view.
The liability is the increased complexity of drive circuitry.
The method of drive for multiplexed displays is essentially a time division multiplex with the number of time divisions
equal to twice the number of common planes used in a given format. As is the case with conventional LCDs, in order
to prevent irreversible electrochemical action from destroying the display, the voltage at all segment locations must
be caused to reverse polarity periodically so that zero net DC voltage is applied.
This is the reason for the doubling in time divisions: Each common plane must be alternately driven with a voltage
pulse of opposite polarity.
3
Controlling of Liquid Crystals
This chapter reflects how to control passive LC-segments
3.1
MB963xx Microcontrollers with LCD Controller/Driver
The following microcontrollers in the 16FX Family have integrated line-drivers:
Table 1. MB963xx Microcontrollers with LCD Controller
MCU series
LCD-lines
MB96370
4x72
MB96380
4x65
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F²MC-16FX Family, LC-Display
3.1.1
Internal LCD Controller
The following figure shows the block diagram of the LCD controller of the 16FX Family:
Figure 7. Block Diagram of LCD Controller on MB963xx
The LCD controller/driver has up to 36 8-bit built-in display data memory, and controls the LCD display by means of
four common outputs and 72 segment outputs. Three duty cycle output modes are available; one can be selected
among the same. A LCD panel can be driven directly. The LCD controller/driver provides functions for directly
displaying the contents of display data memory on the LCD panel by means of segment output and common output.
Features:
LCD drive voltage divider resistance is built-in. External divider resistance can also be connected.
Up to 4 common outputs (COM0 to COM3)
Up to 72 segment outputs (SEG0 to SEG71)
36-byte display data memory (display RAM) is built-in
The duty can be selected as 1/2, 1/3, 1/4
Drives the LCD directly
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F²MC-16FX Family, LC-Display
3.1.2
LCD Control Registers
This section describes the list of registers that controls the LCD operation.
The LCR register configures the frame period, duty cycle setting and also controls bias and clock.
Table 2. LCR
bit7
bit0
Register: LCR
CSS
LCEN
Clock
Selection
VSEL
BK
MS1
Int./Ext.
Bias
DisplayBlanking
MS0
FP1
Display Mode
Duty Cycles
FP0
Frame Period
Note: MS0-MS1 bits will decide which of the COM lines among COM0 to COM3 needs to be interfaced to the LCD
glass. However, the unused COM lines cannot be used as general purpose I/O lines or any other shared resource
lines since it always outputs some signal (as shown in hardware manual) irrespective of the configured duty cycle.
Hence up to two port pins needs to be compromised.
The LECR register also controls the clock.
Table 3. LECR
bit7
bit0
Register: LECR
CKSEL
Clock
Selection
Table 4. LCDCMR
bit7
bit0
Register: LCDCMR
DTCH
COM3
Bias Control
COM2
COM1
COM0
Common Driver Enable
Note: It should be noted that in order to use LCD, LCDCMR register needs to be set to a value equal to 0x0F. Setting
any other value than this will not enable the LCD.
The LCDERn registers enable the LCD (SEGxx) segment outputs. If there are 72 LCD segments (x = 72) then there
are 9 (x/8-1) such registers form LCDER0 to LCDER8. Each bit is corresponding to one LCD segment. If the bit is 0
then the LCD segment is disabled else it is enabled.
bit7
bit0
Register: LCDER0
SEG7
SEG6
SEG5
SEG4
SEG3
SEG2
SEG1
SEG0
LCD Segment Enable
•
•
•
Table 5. LCDER
bit7
bit0
Register:
LCDER(x/8-1)
…
SEG(x-1)
SEG(x-8)
LCD Segment Enable
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F²MC-16FX Family, LC-Display
The LCDVER register enables the V0 to V3 pins to input the external bias. It should be noted that pins V0 to V3 are
shared with some of the segment lines. Hence if any of the V0 to V3 pins is used, then the corresponding segment
lines would be disabled and cannot be used.
Table 6. LCDVER
bit7
bit0
Register: LCDVER
V3
V2
V1
V0
LCD Voltage Enable
As discussed before, there can be up to 36 8-bit built-in display RAM. The total number VRAM registers depends on
the total number of LCD segments. Considering 65 segments, there would be such 33 VRAM registers from VRAM0 to
VRAM32. Each VRAM register controls two consecutive LCD segment lines.
e.g. VRAM0 register controls LCD segment line 0 and 1. Bits DL0 to DL3 corresponds to segment line 0 and DH0 to
DH3 corresponds to segment line 1.
Bit DL0 should be set to 1, if the LCD segment at the junction of COM0 and SEG0 is to be lit.
Bit DL1 should be set to 1, if the LCD segment at the junction of COM1 and SEG0 is to be lit.
Bit DL2 should be set to 1, if the LCD segment at the junction of COM2 and SEG0 is to be lit.
Bit DL3 should be set to 1, if the LCD segment at the junction of COM3 and SEG0 is to be lit.
Bit DH0 should be set to 1, if the LCD segment at the junction of COM0 and SEG1 is to be lit.
Bit DH1 should be set to 1, if the LCD segment at the junction of COM1 and SEG1 is to be lit.
Bit DH2 should be set to 1, if the LCD segment at the junction of COM2 and SEG1 is to be lit.
Bit DH3 should be set to 1, if the LCD segment at the junction of COM3 and SEG1 is to be lit. So on and so forth.
Table 7. VRAM
bit7
bit0
Register: VRAM0
DH3
DH2
DH1
DH0
DL3
Segment 1 Control
DL2
DL1
DL0
Segment 0 Control
•
•
•
Register: VRAM(x/2-1)
bit7
DH3
DH2
DH1
DH0
DL3
Segment x Control
bit0
DL2
DL1
DL0
Segment x-1 Control
The LCD drive voltage is controlled either by external voltage divide resistors or internal voltage divide resistors. If the
internal voltage divide resistors are to be used, VSEL bit of LCR register needs to be set to 1. In this case all the
segment lines those are shared with V0 to V3 can be used.
The brightness can be controlled by connecting a variable resistor between the VCC and V3 pins. Also the V3 bit of
LCDVER register needs to be set to 1. In this case the segment line which is shared with the V3 cannot be used.
If the external voltage divide resistors are to be used, LCDVER register needs to be set to a value of 0x0F. In this
case none of the segment lines those are shared with V0 to V3 can be used.
The circuit diagrams for above three cases are discussed in the hardware manual.
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F²MC-16FX Family, LC-Display
3.1.3
I n t e r f a c i n g M B 9 6 3 8 x t o L C D G l a s s vi a O n - c h i p L C D C o n t r o l l e r
The below connection diagram shows interfacing of MB9638x to DE133 series LCD (of Display Elektronik GmbH
make). Here 3 COM lines and 24 SEG lines are used. Hence total 72 segments can be addressed. LCD controller is
required to be used in ⅓ Duty Cycle mode.
It should also be note that the frame period (which is set by LCR:FP) of the LCD controller should be within the
allowable driving frequency of LCD glass. For DE133 the driving frequency range is 30 Hz to 100 Hz.
Figure 8. Interfacing MB9638x to LCD DE133
SEG0
SEG1
SEG2
SEG3
SEG4
SEG5
SEG6
SEG7
SEG8
SEG9
SEG10
SEG11
SEG12
SEG13
SEG13
SEG14
SEG15
SEG16
SEG17
SEG18
SEG19
SEG20
SEG21
SEG22
SEG23
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
COM0
COM1
COM2
25
26
27
DE133
MB9638x
The example which illustrates the software part of this interfacing is discussed in section 4.1.
3.2
External LCD Controller/Driver
Some semiconductor companies offer different kinds of external LCD-controllers. The functionality is more or less the
same but differences can be found in number of Common-/Segment-lines and of course the interface circuitry to the
microcontroller.
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F²MC-16FX Family, LC-Display
3.2.1
I n t e r f a c i n g M B 9 6 3 x x t o L C D G l a s s vi a E x t e r n a l L C D C o n t r o l l e r
The PCF8576 is a single-chip LCD-controller from Philips with included LCD-driver and data-RAM for up to 160
segments. By only 2-wires it can easily be connected to the microcontroller.
Figure 9. Interfacing MB963xx to LCD Glass via PCF8576
VCC
SDA
SCL
PCF8576
MB963xx
VSS
Here an uncompleted list of manufactures for external LCD-controllers:
Table 8. List of LCD Controller Manufacturer
Company
3.3
Web-site
Remark
Hitachi
www.hitachi.com
miscellaneous
Holtek
www.holtek.com
HT162x (4x32 … 8x64Segments)
MAXIM
www.maxim-ic.com
miscellaneous
NXP/Philips
www.nxp.com
I2C-interface: PCF8576 (4x40)
SAMSUNG
www.samsungelectronics.com
miscellaneous
Alphanumeric LCD Module
In some applications it is required to display alphabets (a,b,A,B etc.) and symbols (@, #, , etc.) along with
numbers (1,2,3 etc.). The LCD glass explained in section 3.1.3 cannot be used since it can only display only numbers
and some alphabets. In such cases, it is required to use alphanumeric LCD module.
There are a plenty of such LCD modules available. These modules include LCD Controller as well as segment
drivers. Additionally it provides a simple parallel interface to establish communication with a microcontroller. In mostly
all modules, the HD44780 or derivative can be found. Hitachi Semiconductor settled like a standard with introducing
this controller that makes it easy to use software libraries.
Up to 80 alphanumeric characters can be displayed, very common are displays in configurations like 2x14, 2x16,
2x20, 2x24, 2x40 and 4x20 characters.
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F²MC-16FX Family, LC-Display
3.3.1
I n t e r f a c i n g M B 9 6 3 x x t o L C D M o d u l e vi a I / O P o r t s
For interfacing MB963xx to LCD Module HD44780 only seven digital I/O pins have to be reserved. Figure 10 shows
how to connect such a standard LCD module. In this example, port 00 is used, but any other port can be used, too.
The display supports two modes: Three Control-Lines (E, R/W, RS) are used, but for the data 4 or 8 data-lines can be
used. In order to minimize the number of port-pins this example works in 4-bit mode. Every data byte is transmitted in
two nibbles using a handshake protocol.
Figure 10. Interfacing MB963xx to HD44780
O
P00_0
RS
O
P00_1
R/W
O
P00_2
E
Alphanumerical LCD
(HD44780)
4
5
11 12 13 14
3
+5V
V0
MB963xx
P00_4
I/O
GND
D
0
D
/1
D
D
/2
4
D
D
/3
5
D
/
6
D
7
6
P00_5
I/O
P00_6
I/O
Contrastadjustment
P00_7
I/O
The example which illustrates the software part of this interfacing is discussed in section 4.2.
+
5
V
G
N
D
The same pin-out can be found at the most modules:
Table 9. HD44780 Pin Description
Pin
Symbol
Level
I/O-Function
Function (8-bit mode)
Function (4-bit mode)
1
Vss
-
-
Power supply (GND)
Power supply (GND)
2
Vcc
-
-
Power supply (+5V)
Power supply (+5V)
3
Vee
-
-
Contrast adjust
Contrast adjust
4
RS
0/1
I
0 = Instruction 1 = data
0 = Instruction 1 = data
5
R/W
0/1
I
0 = Write to 1=Read from LCD
0 = Write to 1=Read from LCD
6
E
10
I
Enable signal
not used
2 Enable signal
7
D0
0/1
I/O
Data bus line 01(LSB)
8
D1
0/1
I/O
Data bus line 1
not used
9
D2
0/1
I/O
Data bus line 2
not used
10
D3
0/1
I/O
Data bus line 3
not used
11
D4
0/1
I/O
Data bus line 4
Data bus line 0 (LSB) and 4
12
D5
0/1
I/O
Data bus line 5
Data bus line 1 and 5
13
D6
0/1
I/O
Data bus line 6
Data bus line 2 and 6
14
D7
0/1
I/O
Data bus line 7 (MSB)
Data bus line 3 and 7 (MSB)
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F²MC-16FX Family, LC-Display
An initial sequence has to be sent to the module in order to select the 4bit interface as well as some basic displaysettings. Data transfer between the controller and the LCD consists of instructions or data (ASCII-compatible
character set).
Table 10. HD44780 Commands
Instruction
R
S
RW
DB
7
DB
6
DB
5
DB
4
DB
3
DB
2
DB
1
DB
0
Description
Clear display
0
0
0
0
0
0
0
0
0
1
Clears display and returns
cursor home
Cursor home
0
0
0
0
0
0
0
0
1
*
Returns cursor to home
position
Entry mode set
0
0
0
0
0
0
0
1
ID
S
Sets cursor move direction
(I/D),
Display On/Off
0
0
0
0
0
0
1
D
C
B
Sets On/Off of all display (D),
cursor
Cursor- / displayshift
0
0
0
0
0
1
SL
RL
*
*
Sets cursor-move or displayshift
Function set
0
0
0
0
1
DL
N
F
*
*
Sets interface data length (DL),
number
Set CGRAM
address
0
0
0
1
a
a
a
a
a
Set DDRAM
address
0
0
1
a
a
a
a
a
a
a
Sets the DDRAM address.
Read busy-flag
0
1
BF
a
a
a
a
a
a
a
Reads Busy-flag (BF) and
address counter
Write to CG- or
DD-RAM
1
0
d
d
d
d
d
d
d
d
Writes data to CGRAM or
DDRAM.
Read from CGor DD-RAM
1
1
d
d
d
d
d
d
d
d
Reads data from CGRAM or
DDRAM.
a
Sets the CGRAM address.
DDRAM = Display Data RAM. CGRAM = Character Generator RAM. a=address. d=data
Table 11. HD44780 Commands Description
I/D: 0=Decrement cursor position,1=Increment cursor position
S: 0 = No display shift, 1 = Display shift
D: 0 = Display off, 1 = Display on
C: 0 = Cursor off, 1 = Cursor on
B: 0 = Cursor blink off, 1 = Cursor blink on
S/L: 0 = Move cursor, 1 = Shift display
R/L: 0 = Shift left 1 = Shift right
DL: 0 = 4-bit interface, 1 = 8-bit interface
N: 0 = 1/8 or 1/11 Duty (1 line), 1 = 1/16 Duty (2 lines)
F: 0 = 5x7 dots, 1 = 5x10 dots
BF: 0=Can accept instruction, 1=Internal operation in progress
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F²MC-16FX Family, LC-Display
4
LCD Examples
Examples for LCD
4.1
Interfacing MB9638x to LCD Glass DE133
The following software example initializes LCD with ⅓ bias and frame period of 40.69 Hz (considering CLKP1 of 4
MHz). Then it initializes display RAM (in accordance with the data to be displayed), enables the LCD in ⅓ duty mode
and displays message.
For the corresponding connection diagram please refer section 3.1.3.
4.1.1
Flowchart
InitLCD()
DispMessage()
Configure LCDVER to disable LCD
reference voltage pins V0 to V3
Configure VRAM0 to VRAM10 registers
to display “FUJITSU”
Message
Configure LCDCMR to enable COM lines
COM0 to COM3 and 1/3 bias
Configure LCR 1/3 bias duty and enable
LCD
Configure LCR to use CLKP1 for frame
period generation, use internal divider
resistors, blank and deactivate LCD
and frame period = 24.576 ms
main()
Initialize interrupt level and enable
interrupts
Configure LCDER0 to LCDER2 registers
with 0xFF to enable Segment lines
SEG0 to SEG23
Call InitLCD()
Call DispMessage()
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F²MC-16FX Family, LC-Display
4.1.2
Code
void InitLCD(void)
{
LCDVER = 0x00;
LCDCMR = 0x0F;
LCR = 0x31;
LCDER0 = 0xFF;
LCDER1 = 0xFF;
LCDER2 = 0xFF;
//
//
//
//
//
//
//
disable V0 to V3
enable COM lines, 1/3 bias
CLKP1, internal divider resistor, blank LCD, deactivate LCD,
frame period = 4 MHz/(2^15*3) = 40.69 Hz
enable SEG0 to SEG7
enable SEG8 to SEG15
enable SEG16 to SEG23
}
void DispMessage(void)
{
VRAM0 = 0x13;
VRAM1 = 0x30;
VRAM2 = 0x34;
VRAM3 = 0x52;
VRAM4 = 0x03;
VRAM5 = 0x30;
VRAM6 = 0x63;
VRAM7 = 0x12;
VRAM8 = 0x27;
VRAM9 = 0x43;
VRAM10 = 0x03;
LCR_MS = 2;
LCR_BK = 0;
// 1/3 duty
// enable LCD
}
void main(void)
{
InitIrqLevels();
__set_il(7);
__EI();
// allow all levels
// globally enable interrupts
InitLCD();
DispMessage();
while(1);
}
4.2
Interfacing MB963xx to LCD Module HD44780
The following software example initializes LCD module HD44780 in 4-bit mode and then displays message.
For the corresponding connection diagram please refer section 3.3.1.
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F²MC-16FX Family, LC-Display
4.2.1
Flowchart
LCDinitdisp()
Clear Port 00 data
Configure pins P00_P0 to
P00_P7 to as digital inputs
LCDoutb()
Enable HD44780 in write
mode by setting E (P00_P2)
and clearing R/W (P00_P1)
Write the 0x02 (Function set:
Interface 4-bit) to HD44780
Data needs to be
written to DDRAM?
Y
Set RS line of HD44780
(P00_P0)
Enable HD44780 in write
mode by setting E (P00_P2)
and clearing R/W (P00_P1)
Call LCDwait() with
parameter short_wait
Write the 0x03 (Function set:
Interface 8-bit) to HD44780
Disable HD44780 by clearing
E (P00_P2)
Call LCDwait() with
parameter short_wait
Call LCDwait() with
parameter short_wait2
Enable HD44780 in write
mode by setting E (P00_P2)
and clearing R/W (P00_P1)
Disable HD44780 LCD by
clearing E (P00_P2)
Call LCDoutb(0x28) for
Function set: Interface 8-bit,
and No. of display lines 2
Write the higher nibble (D4D7) of passed parameter a to
HD44780
Call LCDoutb(LCD_CUROFF)
for Display: ON, Cursor: OFF
and Blinking: OFF
Call LCDwait() with
parameter tiny_wait
Call LCDwait() with
parameter long_wait
Enable HD44780 in write
mode by setting E (P00_P2)
and clearing R/W (P00_P1)
Write the 0x03 (Function set:
Interface 8-bit) to HD44780
Call LCDwait() with
parameter short_wait
Disable HD44780 LCD by
clearing E (P00_P2)
Call LCDwait() with
parameter long_wait
Call
LCDoutb(LCD_NOSHIFT)
for Increment DDRAM and No
Display Shift
Call LCDoutb(LCD_HOME)
for setting DDRAM address to
0x00 (Return Home)
Call LCDoutb(LCD_CLR)
for clearing display
Exit
Enable HD44780 in write
mode by setting E (P00_P2)
and clearing R/W (P00_P1)
N
Clear RS line of HD44780
(P00_P0)
N
Disable HD44780 LCD by
clearing E (P00_P2)
Call LCDbusy()
Enable HD44780 in write
mode by setting E (P00_P2)
and clearing R/W (P00_P1)
Write the lower nibble (D0-D3)
of passed parameter a to
HD44780
Call LCDwait() with
parameter tiny_wait
Disable HD44780 LCD by
clearing E (P00_P2)
Write the 0x03 (Function set:
Interface 8-bit) to HD44780
Call LCDbusy()
Call LCDwait() with
parameter short_wait
Exit
Disable HD44780 LCD by
clearing E (P00_P2)
Call LCDwait() with
parameter long_wait
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Document No. 002-04779Rev.*A
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F²MC-16FX Family, LC-Display
LCDbusy()
LCDgoto(address)
LCDprint(*Name2)
Clear Port 00 data before
reading
Enable HD44780 in write
mode by setting E (P00_P2)
and clearing R/W (P00_p1)
Find the length of the string
pointed by *Name2 and store
in l
Write the higher nibble (D4D7) of passed address to
HD44780
Get the next character in the
string and store in c
Enable input on pins P00_P4
to P00_P7
Configure pins P00_P4 to
P00_P7 to as digital inputs
Enable HD44780 in read
mode by setting E (P00_P2)
and R/W (P00_P1)
Call LCDwait() with
parameter short_wait
Y
Read the higher nibble (D4D7) from HD44780
Disable HD44780 LCD by
clearing E (P00_P2)
Enable HD44780 LCD again
by setting E (P00_P2)
Read the lower nibble
(D0-D3) from HD44780
Disable HD44780 LCD by
clearing E (P00_P2) also clear
R/W (P00_P1)
Disable HD44780 LCD by
clearing E (P00_P2)
N
1
Set the MSB of the same and
store in b
Enable HD44780 in write
mode again by setting E
(P00_P2) and clearing R/W
(P00_P1)
Call LCDoutb(b)
Was that last character in
string pointed by Name2?
Write the lower nibble (D4-D7)
of passed address to
HD44780
Y
Disable HD44780 LCD by
clearing E (P00_P2)
Exit
1
to set RS line in order to
write to DDRAM in function
LCDoutb())
Clear port 00 data (D0-D7)
Call LCDbusy()
LCDwait(i)
Decrement i
Exit
Configure pins P00_P4 to
P00_P7 to as digital outputs
i = 0?
N
LCD busy (bit D7 =1)?
NOP
Y
N
Exit
Exit
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Document No. 002-04779Rev.*A
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F²MC-16FX Family, LC-Display
4.2.2
Code
lcd.c
#include "lcd.h"
/*****************************************************************************
* Initdisp : Resets the LCD and configures the I/F for 4-Bit bus
*****************************************************************************/
void LCDinitdisp(void)
{
LCD_PDR=0;
/* Port 0 Off
*/
LCD_DDR=0x0FF;
/* Set Port 0 to output */
LCD_PDR=0x34;
/* Startup sequence
*/
LCDwait(short_wait);
LCD_PDR=0x30;
LCDwait(long_wait);
LCD_PDR=0x34;
LCDwait(short_wait);
LCD_PDR=0x30;
LCDwait(long_wait);
LCD_PDR=0x34;
LCDwait(short_wait);
LCD_PDR=0x30;
LCDwait(long_wait);
LCD_PDR=0x24;
LCDwait(short_wait);
LCD_PDR=0x20;
LCDwait(short_wait2);
LCDoutb(0x028);
/* Switch to 4-bit mode */
LCDoutb(LCD_CUROFF);
/* No Cursor
*/
LCDoutb(LCD_NOSHIFT);
/* No display shift
*/
LCDoutb(LCD_HOME);
/* Cursor home
*/
LCDoutb(LCD_CLR);
/* Display clear
*/
}
/******************************************************************************
* OUTB
sends one byte to the display
* PARAMETERS:
8-bit data
* RETURNS:
None
*****************************************************************************/
void LCDoutb(unsigned char a)
{
unsigned char b;
b = (a & 0x70);
/* upper nibble
*/
if (a & 0x80)
/* check MSB
*/
{
b = (b | 0x01);
/* set RS line
*/
}
b = (b | 0x04);
/* set E line
*/
LCD_PDR = b;
/* send to LCD
*/
LCDwait(tiny_wait);
b = (b & 0xFB);
/* clear E line
*/
LCD_PDR = b;
/* send to LCD
*/
LCDwait(tiny_wait);
b = (a & 0x0F);
b = b << 4;
if (a & 0x80)
{
b = (b | 0x01);
}
b = (b | 0x04);
LCD_PDR = b;
LCDwait(tiny_wait);
b = (b & 0xFB);
LCD_PDR = b;
LCDbusy();
/* lower nibble
*/
/* to upper nibble */
/* check MSB
*/
/* set RS line
*/
/* set E line
*/
/* send to LCD
*/
/* clear E line
*/
/* send to LCD
/* check LCD
*/
*/
}
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Document No. 002-04779Rev.*A
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F²MC-16FX Family, LC-Display
/*****************************************************************************
* BUSY
polls the busy-line (waits for the LCD to be ready)
* PARAMETERS:
None
* RETURNS:
None
*****************************************************************************/
void LCDbusy(void)
{
unsigned char b;
LCD_PDR = 0;
/* Port Off before reading ! */
b = 0x80;
while (b & 0x80)
/* LCDwait for Busy-line
*/
{
LCD_DDR = 0x0F;
/* set Bus as input to read LCD-busy-flag (LCD_D3) */
LCD_PDR = 0xF6;
/* busy request
*/
LCDwait(short_wait);
b = LCD_PDR;
/* read Port
*/
LCD_PDR_P02 = 0;
LCD_PDR_P02 = 1;
/* toggle E
*/
LCD_PDR_P02 = 0;
LCD_PDR_P01 = 0;
LCD_DDR = 0xFF;
/* reset Port to output
*/
}
}
/*****************************************************************************
* GOTO
jump cursor to address
* PARAMETERS:
address
* RETURNS:
None
*****************************************************************************/
void LCDgoto(unsigned char address)
{
LCD_PDR = (address & 0xF0) | 0x04;
/* upper nibble, set E line */
LCD_PDR_P02 = 0;
/* clear E line
*/
LCD_PDR = ((address<<4) & 0xF0) | 0x04;
/* lowe nibble, set E line
*/
LCD_PDR_P02 = 0;
/* clear E line
*/
LCD_PDR = 0;
LCDbusy();
}
/*****************************************************************************
* PRINT
displays a string
* PARAMETERS:
pointer to string
* RETURNS:
None
*****************************************************************************/
void LCDprint(char *Name2)
{
unsigned char c;
unsigned char b;
unsigned short i,l;
l=strlen(Name2);
for (i=0; i<l; i++)
{
c=(Name2[i]);
/* go through string */
/* pick char
*/
b=(c | 0x80);
LCDoutb(b);
}
}
/*****************************************************************************
* VERY PRIMITIVE DELAY LOOP *
*****************************************************************************/
void LCDwait(unsigned long i)
{
while(i--)
__asm("\tNOP");
}
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Document No. 002-04779Rev.*A
19
F²MC-16FX Family, LC-Display
lcd.h
/*******************************************************************
LCD.H
Prototypes and constants for functions
*******************************************************************/
#ifndef _LCD_H
#define _LCD_H
/* LCD Port */
#define LCD_PDR
#define LCD_DDR
#define LCD_PDR_P01
#define LCD_PDR_P02
PDR00
DDR00
PDR00_P1
PDR00_P2
/* Control defines (use with LCDoutb) : */
#define LCD_CLR
0x01
#define LCD_HOME
0x03
#define LCD_CUROFF
0x0C
#define LCD_CURON
0x0F
#define LCD_NOSHIFT
0x06
#define LCD_1st_line
0x80
#define LCD_2nd_line
0xC0
#define LCD_3rd_line
0x94
#define LCD_4th_line
0xD4
/* Prototypes */
void LCDinitdisp(void);
void LCDoutb(unsigned char);
void LCDgoto(unsigned char address);
void LCDprint(char *Name2);
void LCDprintnum(int n);
void LCDprinthex(unsigned long n, unsigned char digits);
void LCDmovscr(char *Name2, unsigned long delay);
void LCDwait(unsigned long i);
void LCDbusy(void);
/* Wait
#define
#define
#define
#define
times (depends on used MCU speed) */
tiny_wait
20
short_wait 400
short_wait2 700
long_wait
50000
#endif /* LCD_H */
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Document No. 002-04779Rev.*A
20
F²MC-16FX Family, LC-Display
main.c
void main(void)
{
unsigned char ch;
InitIrqLevels();
__set_il(7);
__EI();
/* allow all levels */
/* globally enable interrupts */
LCDinitdisp();
/* initialize the LC display */
LCDgoto(LCD_1st_line);
LCDprint("
XXX
"); /*Display message*/”
LCDgoto(LCD_2nd_line);
LCDprint("YYY");
/*Display message*/”
while (1);
}
5
Conclusion
This chapter summarizes the results of the different control-mechanism of LCD.
The most useful way how to control a LCD depends very much on the application.
For industrial and automotive application, where lifetime and temperature influence is a very important point, a
dedicated LCD-controller should be used. A microcontroller with built-in LCD-controller may help to save costs,
because no further external components are necessary. In case that a big number of segments have to be controlled,
then an external LCD-controller is indispensable.
If the application requires displaying text-messages then alphanumeric LC-modules will be a good choice, because
hardware and software overhead can be reduced.
6
Additional Information
Information about Cypress Microcontrollers can be found on the following Internet page:
http://www.cypress.com/cypress-microcontrollers
The software example related to this application note is:
96380_lcd_glass
96340_lcd_module
It can be found on the following Internet page:
http://www.cypress.com/16lx
www.cypress.com
Document No. 002-04779Rev.*A
21
F²MC-16FX Family, LC-Display
7
Document History
Document Title: AN204779 - F²MC-16FX Family, LC-Display
Document Number:002-04779
Revision
**
*A
www.cypress.com
ECN
-
5084284
Orig. of
Change
NOFL
NOFL
Submission
Date
Description of Change
07/20/2007
Initial release
09/07/2007
Updated the entire document with review findings from PHu,
04/14/2016
Migrated Spansion Application Note MCU-AN-300230-E-V11 to Cypress
format
Document No. 002-04779Rev.*A
22
F²MC-16FX Family, LC-Display
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© Cypress Semiconductor Corporation, 2007-2016. This document is the property of Cypress Semiconductor Corporation and its subsidiaries, including
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Cypress reserves the right to make changes to this document without further notice. Cypress does not assume any liability arising out of the application
or use of any product or circuit described in this document. Any information provided in this document, including any sample design information or
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Document No. 002-04779Rev.*A
23