hitachi hd44780 lcd display manufacturer

The Hitachi HD44780 LCD controller is an alphanumeric dot matrix liquid crystal display (LCD) controller developed by Hitachi in the 1980s. The character set of the controller includes ASCII characters, Japanese Kana characters, and some symbols in two 40 character lines. Using an extension driver, the device can display up to 80 characters.

The Hitachi HD44780 LCD controller is limited to monochrome text displays and is often used in copiers, fax machines, laser printers, industrial test equipment, and networking equipment, such as routers and storage devices.

Compatible LCD screens are manufactured in several standard configurations. Common sizes are one row of eight characters (8×1), and 16×2, 20×2 and 20×4 formats. Larger custom sizes are made with 32, 40 and 80 characters and with 1, 2, 4 or 8 lines. The most commonly manufactured larger configuration is 40×4 characters, which requires two individually addressable HD44780 controllers with expansion chips as a single HD44780 chip can only address up to 80 characters.

Character LCDs may have a backlight, which may be LED, fluorescent, or electroluminescent. The nominal operating voltage for LED backlights is 5V at full brightness, with dimming at lower voltages dependent on the details such as LED color. Non-LED backlights often require higher voltages.

Character LCDs use a 16-contact interface, commonly using pins or card edge connections on 0.1 inch (2.54 mm) centers. Those without backlights may have only 14 pins, omitting the two pins powering the light. This interface was designed to be easily hooked up to the Intel MCS-51 XRAM interface, using only two address pins, which allowed displaying text on LCD using simple MOVX commands, offering cost effective option for adding text display to devices.

Vee (also V0): This is an analog input, typically connected to a potentiometer. The user must be able to control this voltage independent of all other adjustments, in order to optimise visibility of the display that varies i. a. with temperature and, in some cases, height above the sea level. With a wrong adjustment, the display will seem to malfunction.

R/W: In most applications, reading from the HD44780 is not necessary. In that case, this pin can be permanently connected to ground and no processor pins need to be allocated to control it.

Selecting 4-bit or 8-bit mode requires careful selection of commands. There are two primary considerations. First, with D3–D0 unconnected, these lines will always appear high (binary 1111) to the HD44780 since there are internal pull-up MOSFETs.

The execution times listed in this table are based on an oscillator frequency of 270 kHz. The data sheet indicates that for a resistor of 91 kΩ at VCC=5 V the oscillator can vary between 190 kHz and 350 kHz resulting in wait times of 52.6 µs and 28.6 µs instead of 37 µs. If a display with the recommended 91 kΩ resistor is powered from 3.3 volts the oscillator will run much slower. If the busy bit is not used and instructions are timed by the external circuitry, this should be taken into account.

The original HD44780 character generator ROM contains 208 characters in a 5×8 dot matrix, and 32 characters in a 5×10 dot matrix. More recent compatible chips are available with higher resolution, matched to displays with more pixels.

Modern Character LCD display modules have been possible since 1987 when Hitachi introduced the HD44780 LCD controller. Since then, Hitachi no longer manufactures this integrated circuit (IC), but modern LCD controller ICs make it a point to be HD44780-compatible.

The character LCD display modules offered by Crystalfontz America Inc. are no exception to this compatibility standard. This assures backwards compatibility with existing product infrastructure for our customers.

From time to time, we are asked to find a suitable replacement for an older LCD display. When our customer sent us the just-barely functional display in question to help verify we did have a compatible display we were delighted (in only the way Engineers can get delighted) that the old display had an old-school HD44780 controller.

Since the display was operational, we were able to find a suitable replacement for our customer. A few modifications were necessary to drive the backlight properly in the device the display is for, but otherwise, the display was functionally the same, thanks to the HD44780 compatible controller.

This gave us an opportunity to see the changes in how Character LCD displays are manufactured and assembled. The controller and drivers ICs are no longer discreet IC — they are bonded to the PCB and then covered with ‘blobs” to protect them. (Learn more about blobs on LCDs.) The improvements in PCB layout, design, and manufacturing are very apparent.

We invite you to contact our helpful customer support team via chat, phone, or email — to see what display will best suit your needs or answer any questions our LCD, TFT, and OLED modules.

Dot Matrix Liquid Crystal Display Controller/DriverModules HD44780UA00TS,Holtek, HD44780UA01FS,HITACHI, DS1000,DALLAS,IC 8SOIC TUBE HD44780UAOOFS,HITACHI,In Stock

Abstract: hitachi hd44780 lcd HD44780 lcd display hd44780 lcd HITACHI HD44780 DOT MATRIX LCD MODULE 14 pin lcd 00001111B hd44780 lcd controller hd44780 lcd controller pin out hitachi hd44780 display

Text: Interfacing an SX Microcontroller to a Hitachi LCD Display Application Note: Simple , ) Interfacing an SX Microcontroller to a Hitachi LCD Display LCD Display Initializing the LCD On power-up, the LCD needs several milliseconds , LCD Display Writing Commands and Data The lcd_write_command and lcd_write_data subroutines use , ;- Interfacing an SX Microcontroller to a Hitachi LCD Display Waiting for the Busy Flag

Abstract: KP-03 LCD hitachi hd44780 16 pin hd44780 display HITACHI HD44780 DOT MATRIX LCD MODULE Hitachi HD44780 LCD LCD MODULE kp kp-03 HD44780 LCD display lcd 2 x 16 HD44780

Text: HITACHI LCD MODULE 16 CHARACTER, 2 LINE DISPLAY Marked KP-01 or KP-03 on top , HC COMPATIBLE Hitachi LCD Display , Page 1 of 4, 17 Nov 1998, Bob Lineberry 68HC11, A13 VSS G A15 G1* G2* Hitachi LCD Display , Page 2 of 4, 17 Nov 1998, Bob , line. Hitachi LCD Display , Page 3 of 4, 17 Nov 1998, Bob Lineberry INSTRUCTION SET , cursor address position. Hitachi LCD Display , Page 4 of 4, 17 Nov 1998, Bob Lineberry -

Text: 3658 Serializing an LCD Display Abstract: Besides reducing the number of required GPIO , Maxim > App Notes > DISPLAY DRIVERS Keywords: LCD driver, op amp, I/O port expander, contrast , LCD character displays connect to the outside world through a controller IC, such as the LCD display . To do , also provides digital control of the LCD "s contrast and backlight intensity. A versatile I/O-port

Text: 3658 Serializing an LCD Display Abstract: Besides reducing the number of required GPIO , Maxim > App Notes > Display Drivers Keywords: LCD driver, op amp, I/O port expander, contrast , LCD character displays connect to the outside world through a controller IC, such as the LCD display . To do that, use the following equations to calculate resistor values R1, R5, and R6 , also provides digital control of the LCD "s contrast and backlight intensity. A versatile I/O-port

Text: from One Port Features and Overview · Uses the industry standard Hitachi LCD display driver , the industry standard Hitachi LCD display driver chip, but will work , interface to an industry standard Hitachi HD44780A LCD controller. This type of display has a simple , to interface to the LCD display module. Bargraph Selects whether the bargraph functions are , function to display string at current ; LCD cursor position. Parameters: sRamString: A pointer to a

Text: industry-standard Hitachi LCD display driver chip protocol Requires only seven I/O pins on one I/O , you can create and display your own custom characters. When to Use a Character LCD Use the Character LCD component to display text data to the user of the product or to a developer during design and , on the LCD module"s display Turns off the LCD module"s display Prints a null-terminated string to the , : Return Value: Side Effects: Turns off the display of the LCD screen. None None None void

Abstract: lcd 2X16 hitachi 2X16 lcd module hd44780 lcd custom HITACHI LCD MODULE lcd display 2x16 software command lcd 2x16 command software 2x16 lcd pin diagram 2X16 hitachi Hitachi HD44780 LCD

Text: industry-standard Hitachi LCD display driver chip protocol Requires only seven I/O pins on one I/O , you can create and display your own custom characters. When to Use a Character LCD Use the Character LCD component to display text data to the user of the product or to a developer during design and , off the LCD Turns on the LCD module"s display Turns off the LCD module"s display Prints a , LCD_Char_DISPLAY_2_LINES_5x10 Return Value: Side Effects: None None Clear display Return cursor and LCD to home

Abstract: lcd custom 2X16 lcd PIN OUT lcd 2x16 HD44780 LCD ASCII CODE c source code 2X16 lcd 4 bit interface character LCD PSoc hitachi 44780 HITACHI LCD MODULE

Text: industry-standard Hitachi LCD display driver chip protocol Requires only seven I/O pins on one I/O , you can create and display your own custom characters. When to Use a Character LCD Use the Character LCD component to display text data to the user of the product or to a developer during design and , the LCD module"s display Turns off the LCD module"s display Prints a null-terminated string to the , ) Description: Parameters: Return Value: Side Effects: Turns off the display of the LCD screen. None None None

Abstract: lcd custom character LCD PSoc HD44780 lcd display hitachi hd44780 lcd 2x16 HD44780 14 pin lcd display 2x16 16 pin diagram of lcd display 2x16 device code 150a HD*4780

Text: industry-standard Hitachi LCD display driver chip protocol Requires only seven I/O pins on one I/O , you can create and display your own custom characters. When to Use a Character LCD Use the Character LCD component to display text data to the user of the product or to a developer during design and , off the LCD Turns on the LCD module"s display Turns off the LCD module"s display Prints a , LCD_Char_DISPLAY_2_LINES_5x10 Return Value: Side Effects: None None Clear display Return cursor and LCD to home

Abstract: IOW56 graphic lcd initialisation KS0108 connector 64X128 graphics lcd 640X256 AX1520 LCD GRAPHIC MODULE 256*64 LH155BA5 LCD 2x8, 10 pin Module

Text: display modules. Since the LCD modules dominate the market of display modules we will talk about LCD , fluorescense displays (VFDs) as well. 1.1 Display Module Variants LCD modules can be sorted into a number of , IO-Warrior, September 21st 2006 1 AN5: Driving Display Modules with IO-Warrior Alphanumeric: display memory in display up to 128 characters in two lines and it can overlay this with

Text: Interfacing the H8/3334Y and the LCD driver 23/10/96 Description In the following code example a H8/3334Y 8-bit microcontroller drives the LCD controller and a character , also see application note APPS/026/1.0 for a description of the interface to display , . Interfacing the H8/3334Y and the LCD driver Hardware Implementation Two I/O ports of the H8/3334Y, which Pins P8,0 to P8,2 are used to control the function of LCD character

Text: Interfacing the H8/3334Y and the LCD driver In the following code example a H8/3334Y 8-bit microcontroller drives the LCD controller and a character display via general I/O ports. The code example , . All other LCD modules based on LCD Driver and Display LM086ALN 8 , description of the interface to display driver. This application note can be used for H8 , , of which Pins P8,0 to P8,2 are used to control the function of LCD

Text: particular LCD (or compatible) display here: LCD -107.pdf Pros and Cons for this LCD , Directly Supported by the Serial Wombat: WD-C2401P 24 x 1 LCD Panel 2x24 Display w/ EL , Display Information 1/14/08 3:23 PM Serial Wombat a general-purpose digital interface device for hobbyists, engineers and students Serial Wombat Home WD-C2401P LCD LCD Purchase A Wombat LCD panel With EL backlight This is a used, 24 character by two line

Text: ) Description The LCD-n ( HD44780A) dot matrix liquid crystal display controller & driver LSI displays , condition for the LCD output level is specified in LCD v o lta g e V lcd ". HD44780A(LCD-H) Display data RAM (DD RAM) The display data RAM (DD RAM , Brisbane, CA 94005-1819 · (415) 589-8300 131 HD44780A(LCD-II) 2. 16-character display using , internal shift re g ister, the display . The rest displays, corresponding to latter

Abstract: 16 pin diagram of HD44780 lcd display 16x2 16x2 lcd method LCD display module 16x2 characters HD44780 16 pin diagram of lcd display 16x2 LCD ASCII CODE 16x2 16x2 lcd HD44780 HITACHI HD44780 DOT MATRIX LCD MODULE hitachi 16x2 lcd LCD display module 16x2 HD44780

Text: · This Application Note provides Character Liquid Crystal Display ( LCD ) driver routines (coded , character LCD display . This 16 x 2 character LCD uses the industry-standard 4-bit data transfer mode. With , initialize the LCD controller, (specific to the type of display ). · Turn the display ON and OFF. · , . · Write a user-defined pixel map in LCD CGRAM from the table. · Display user-defined , following main units: · · Discussion Liquid Crystal Display ( LCD ) is a useful medium of communication

Abstract: 16x2 lcd HD44780 hitachi 16x2 lcd LCD ASCII CODE 16x2 LCD ASCII table CODE 16x2 HD44780 16x2 16x2 lcd HD44780 16x1 LCD command lcd display 16x2 LCD display module 16x2 HD44780

Text: character LCD display that is fitted with a Hitachi LCD uses the , a Typical HD44780-Based Character LCD Module Liquid Crystal Display ( LCD ) is a very useful , controller to control various features of its display . An LCD with a controller is referred to as an LCD , eZ80Acclaim! MCU is a 16x2 character LCD controlled by the LCD Module, with its on-board

Abstract: 16 pin hd44780 display hd44780 LCD 4 20 LCD 16 BY 2 HD44780 hd44780 LCD lcd screen interfacing hd44780 lcd controller HD44780 application LCD HD44780 LCD ASCII CODE

Text: /329-4700 · Fax: 781/326-8703 · www.analog.com T Interfacing an LCD to a , accepts data from the MicroConverter and communicates with the LCD screen. LCD screens , . INTERFACING AN LCD The data bus that connects the LCD to a MicroConverter In assembly code, this interface is , .7 P2.6 P3.6 P0 040H ;Char buffer for LCD CONFIGURING THE LCD SCREEN To display text to the LCD

Abstract: KS0066U HD44780 ADDRESS DDRAM LCD 20X4 HITACHI HITACHI Character LCD Modules 20X4 TABLE DDRAM LCD 20X4 HITACHI Samsung KS0066u HD44780 16x1 LCD 16X4 LCD command hd44780 lcd controller pin out 20x2 display

Text: Step By Step Initialization Flow Chart for LCD Modules. (These , Initialization Flow Chart for LCD Modules. (These instructions are intended to help , Initialization Flow Chart for LCD Modules. (These instructions are intended to help , Step By Step Initialization Flow Chart for LCD Modules. (These instructions , Flow Chart for LCD Modules. (These instructions are intended to help get up

Text: ^ H IT A C H I" UQUIDCRYSIAL DISPLAY MODULES AND DEVCES The Clear Advantage In LCD Technology 4 , : LCD Modules-These consist of the liquid crystal display plus built-in driver circuitry. Some also , 12 Segment LCD M o d u le s page 12 LCD Devices-These consist of the liquid crystal display itself , it many advances over previous display technologies. Even today, the TN LCD continues to enjoy , . T h in Film Transistor (T F T ) The TFT LCD is Hitachi" s premier fla: panel display technology. TFT

Abstract: AND491GST hd44780 AND721GST-LED AND721GST lcd 2 x 16 HD44780 FE0501W Hitachi 2 x 16 character display with backlight AND491GST-LED AND591GST

Text: a-Si Technology Small TFT Color Monitors Large and Medium TFT Color Modules Intelligent LCD Graphic Displays Intelligent LCD Alphanumeric Displays Panel/Segment Displays Film Super Twist Nematic Super , colors 8bit=16.2M colors Note 3: Wide Viewing angle display Purdy Electronics Corporation · 720 , Backlight AND081GST 1x8 4.45 x 8.35 48.0 x 13.0 60 x 36 x 10 5 AND081GST-LED 1x8 4.45 x 8.35 48.0 x 13.0 60 x 36 x 13 5 AND082GST 2x8

Abstract: MOBILE LCD DISPLAY hd44780 LCD 4 20 hd44780 lcd HD44780 hd44780 lcd controller display controller hd44780 LCD hd44780 lcd controller Verilog HD44780 lcd display

Text: Interface Key signals · 32 bit APB bus · LCD Display Controller Interface ­ support of LCD Interface Ports · 32 bit APB bus interface · LCD Display Controllers , Product Technical Brief Date: 05/2001 picoPACKTM LCD Display Controller Interface Introduction Architecture The LCD Display Controller Interface is a synthesiz- for display control , typical LCD display controllers. In addition, the module APB Control Lcd Interrupt Interrupt

Abstract: 2X16 lcd module hd44780 LCD 4x20 HITACHI lcd 2x16 HD44780 2X16 lcd module hd44780 controller pin diagram of lcd display 2x16 lcd 2x16 HD44780 14 pin 4X40 LCD HD44780 HD*4780 16 pin diagram of lcd display 2x16

Text: . 21 Interfacing MB963xx to LCD Module Display ( LCD ) by a microcontroller. Further, the connection to LCD glass and also to , -bit built-in display data memory, and controls the LCD display by means of four common outputs and 72 segment , Controlling of Liquid Crystals contents of display data memory on the LCD panel by means of segment output , Controller The below connection diagram shows interfacing of MB9638x to DE133 series LCD (of Display

Text: Driver) DESCRIPTION The LCD - II ( HD44780A) is a dot matrix liquid crystal display , matrix liquid crystal display systems with less number of chips by using the LCD-II ( HD44780A). , D44780A(LCD-II) · Both display data and character generator RAMs can be read from the MPU. · , Brisbane, CA 94005-1819 · (415) 589-8300 D44780A(LCD-II) (Left Shift Display ) (Right Shift , 06 16-character display using an HD44100H is as shown below: (digit) 1 2

Text: SEftES HOW TO USE HITACHI"S BUILT-IN CONTROLLER DRIVER LCD-H( DISPLAY , built-in controller LSI. Controller LSI LCD driver , S »rl6 R/W-RSl- 1 i 7" oíkD "ook-C.U I I LCD 7> 40 Ol LCD , Interface of liquid crystal display module, there are three power supply terminals, Vqq, GND, and V0. LCD , display drive to V0 terminal. Since suitable" voltage of power supply for LCD shifts according to

Text: rran g em en t D escription The LCD-H ( HD44780A) d o t m atrix liquid crystal display , €¢ Brisbane, CA 94005-1819 • (415) 589-8300 4780A(LCD-H) Display d a ta RAM (DD RAM , display begins a t th e h e a d position. For exam ple, 8 ch aracters using 1 4780A(LCD-H) 2. 16-character display u sing a n , Display 4. Display Position ♦ DD RAM Address HD44100H Display W hen th e display

Blue 16x2 LCD module featuring 2 rows consisting each of 16 characters. The module is compatible with the Hitachi HD44780 controller, and is commonly used in Arduino and other microcontroller projects.

Blue 16x2 LCD module featuring 2 rows consisting each of 16 characters. The module is compatible with the Hitachi HD44780 controller, and is commonly used in Arduino and other microcontroller projects.

The HD66727, dot-matrix liquid crystal display controller and driver LSI incorporating a key scan function, displays alphanumerics, katakana, hiragana, and symbols. It can be configured to drive a dotmatrix liquid crystal display and control key scan functions under the control of an I2C bus or a clocksynchronized serial microprocessor. A single HD66727 is capable of displaying up to four 12-character lines, 40 segments, and 12 annunciators, and controlling up to a 4-by-8 key matrix, and driving three LED. The HD66727 incorporates all the functions required for driving a dot-matrix liquid crystal display such as display RAM, character generator, and liquid crystal drivers, and it also incorporates a booster for the LCD power supply and key scan functions.

- Clear display, display on/off control, icon and mark control, character blink, white-black inverting blinking cursor, icon and mark blink, return home, cursor on/off, white-black inverting raster-row

LCD character modules are “characteristically” simple display devices known for their very low power consumption, low cost and long-term reliability. They are designed to display alpha-numeric characters in preset patterns and do not have much. In most cases, they are small displays with only 8 or 16 or 32 characters, utilized for status reports and simple communication. It is the most popular display for hobbyist because of its ease of operation.

Orient Display offers many standard sizes including (characters x lines) 8×1, 8×2, 16×2, 16×4 , 20×2, 20×4 , 24×4, 40×4, and many more. Orient Display’s character LCD displays cover small LCD character display modules for tiny devices to large character LCD displays for medical equipments.

Orient Display character LCD modules use industrial standard Hitachi HD44780 controller or compatible controllers such as Sitronix ST7066U, Samsung S6A0069, so they can be quickly integrated into a new product or used as a replacement in your existing products.

The LCD panel technologies include TN, STN, FSTN, FFSTN or VA (Vertical Alignment) types and also with positive mode and negative mode and options of reflective, transflective or transmissive polarizers. There are different LED backlights available in various colors including yellow-green, white, red, blue, green, amber, and RGB LEDs as well as no backlight option.

The viewing angles for these character LCD displays are available with 6:00, 12:00, 3:00, and 9:00. Orient Display offers various IC options of character fonts including English/Japanese, western European, eastern European, Scandinavian European, Cyrillic (Russian), and Hebrew/Arabic. These LCD character modules and LCD modules can be used on industrial and consumer’s applications including printers, microwaves, water machines, medical devices, car and home audio, white goods, game machines, toys, industrial meters, etc.

Please see our character LCD display list here. If you can’t find any in the list, please check with our engineers to search our factory database or have a custom-made option.

This is not official manufacturer"s information. It is distilled from information on many different data sheets and from my own experience. I have never used some of these displays. I have extrapolated what I know about the displays that I have used to the ones that I have just read about. I welcome any suggestions and corrections. Contact information is at the bottom of the page.

The HD44780 type controller chip is used with a wide variety of Liquid Crystal Displays. These LCDs come in many configurations each with between 8 and 80 viewable characters arranged in 1, 2, or 4 rows.

The problem is that there is no way to inform the controller of the configuration of the display that it is driving. The controller operates exactly the same way for all displays and it is up to the programmer of the device that is controlling the LCD controller (usually a host microcontroller) to deal with this situation.

The controller contains 80 bytes of Display Data Random Access Memory which is usually referred to as DDRAM. When the controller is used with a 40 x 2 display (forty characters on each of two rows) the operation is quite straightforward and that operation will be explained first. Each of the other configurations introduces one or more quirks so it is best to understand the operation of the 40 x 2 before proceeding to the description of the operation of any of the others.

This is the most common Memory Map for the 80 bytes of DDRAM in the HD44780 controller. There is another rarely encountered configuration that will be presented later.

Each of these DDRAM memory addresses corresponds to a character position on an attached display, but the specific position varies depending on the configuration of that display. As part of the initialization sequence the display is cleared by storing the ASCII code for a space in each of the 80 memory locations. Subsequently if a different ASCII code is stored in any of those memory locations then the character corresponding to that ASCII code is automatically displayed at a specific location on the display.

You can tell the controller where you want the first ASCII character that you send it to be stored, this is usually address 00h. After receiving that character it will automatically update its address pointer and put the next ASCII character you send into an adjacent memory location with no more addressing work on your part. You can specify whether to increment or decrement the address counter but normally it is incremented, so the next character will be put into address 01h. The LCD controller automatically accounts for the gap in addresses and after storing an ASCII code in address 27h it puts the next code in address 40h. Similarly it increments from address 67h back to 00h.

Here is a simplified diagram of the display on a 40 x 2 LCD Module. Each of the boxes in the diagram represents a location where a character can be displayed.

Here is a copy of the memory map of the controller. Remember, each of the memory locations in the controller chip is directly associated with one of the character locations on the display.

By some miracle of modern technology there is actually a one for one relationship between these two diagrams. If an ASCII code is stored at address 00h in memory the corresponding character will appear at the left end of the top row of the display. If an ASCII code is stored at address 63h in memory the corresponding character will appear five locations in from the right end of the second row of the display.

Here is a diagram showing how the two rows of the display are mapped into the two lines of memory. It is basically a combination of the two diagrams just above.

When the host controller wants to display a string of characters on the display all it has to do is specify a starting DDRAM address and then start sending the string of ASCII codes corresponding to the desired characters to the LCD controller, one after another. The LCD controller takes the first code that it receives, stores it at the specified address, and simultaneously displays the corresponding character on the display. It then increments it"s internal address counter and stores the next ASCII code that it receives in the next DDRAM location which causes the corresponding character to appear in the next location on the display. As mentioned before the LCD controller automatically accounts for the gap in addresses and after storing an ASCII code in address 27h it puts the next code in address 40h. Similarly it increments from address 67h back to 00h.

This display also has 80 characters, but the relationship between the DDRAM addresses and the character locations on the LCD is not quite as straightforward as the LCD with two rows of 40 characters. Here is a diagram of the device.

The memory map is always the same regardless of the display configuration, but in this drawing I have shown a small space between addresses 13h and 14h on the first line and another between addresses 53h and 54h on the second line.

Here is the same memory map, rearranged this time to show how the memory addresses relate to the character positions on a 20 x 4 LCD. Note how the right half of the previous diagram is now below the left half and note the resulting sequence of starting addresses for each display row (00h, 40h, 14h, 54h).

Remember that the LCD controller still considers this to be two lines of RAM. It is important to understand that this way of picturing the DDRAM addresses helps relate the memory addresses to the character locations but does not change the fact that as far as the controller is concerned there are only two lines of memory. In other words, although this diagram shows the DDRAM differently than before, the actual DDRAM configuration and operation is exactly the same as described above for the 40 x 2 display since there is no way of telling the LCD controller that there are now 4 rows of 20 characters instead of 2 rows of 40 characters.

When a long string of ASCII codes is sent to this LCD controller the action is not quite as simple as for the 40 x 2 display. After the first row is full the characters will continue on to the third row. The normal automatic incrementing from 27h to 40h will then cause the display to continue on the second row, and from there it will continue to the fourth row. After that the following characters will appear back on the first row, and so on.

In order to get a coherent display on sequential rows it is necessary to compensate for the design of the LCD controller when programming the host microcontroller. Basically the program on the host microcontroller can keep track of the DDRAM addresses, and when appropriate it can set up a new starting DDRAM address.

For each of the above displays there are 80 addresses in memory and there are 80 character locations on the display so it should be obvious that any time you send an ASCII code to the controller the corresponding character will show up somewhere on the display. If you mess up the address the character may not show up where you expected it, but it will be visible somewhere. If you work back from where it actually appears you can usually figure out where you made your mistake. All of the displays that follow have fewer character locations on the display than memory addresses in the controller. This makes the operation somewhat more complicated and troubleshooting more difficult.

This can be thought of as a truncated 40 x 2 display, but there are some ramifications of this truncation that may not be readily apparent. Here is a drawing of the device.

It is important to understand that, although this diagram shows only the part of the DDRAM that is normally used to display information on the 20 x 2 LCD, the actual memory map and controller operation is exactly the same as described above for the previous displays. Again that is because there is no way of telling the LCD controller that there are only 40 characters on the attached display.

Here is a drawing of the complete memory map. Note that this drawing is the same as the one for the 20 x 4 display except that the addresses on the right side are greyed out.

Although this display has only 40 characters there are still 80 bytes of DDRAM and they are still configured the same as they were before. The greyed out addresses are the locations in DDRAM that do not have corrresponding locations on the display. Any ASCII codes that are written to those locations are not lost, and it is possible to display them by "shifting" the display window, but in normal use as described here they are simply not displayed.

When a long string of ASCII codes is sent to this LCD controller the action is not quite as simple as for either of the 80 character displays. Assume that the host controller is sending a string of characters as described above. Consider what happens after the LCD controller stores an ASCII code in address 13h and displays the corresponding character at the right end of the top row on the LCD. It then stores the next ASCII code in address 14h, which has no corresponding location on this 20x2 display. As more ASCII codes are sent to the LCD controller they are stored in the DDRAM but do not appear on the display until the LCD controller finally increments it"s address counter from 27h to 40h at which time subsequent characters start to appear on the second row of the display. As far as a viewer of the display is concerned there is a gap of 20 missing characters. The same thing will happen on the second row when ASCII codes are stored in addresses 54h - 67h.

In order to prevent any missing characters the program on the host microcontroller can keep track of the DDRAM addresses, and when appropriate it can set up a new starting DDRAM address. On the other hand the display can be shifted to display those missing characters, but the techniques to do that will not be covered here.

This is a commonly found configuration and its operation is almost identical to that of the 20 x 2. The relationship between the DDRAM addresses and the character locations on the LCD is a subset of the example shown above. Here is a drawing of the device.

Once again it is important to understand that although this diagram shows only the part of the DDRAM that is normally used to display information on the 16 x 2 LCD the actual DDRAM configuration and operation is exactly the same as described above for the 40 x 2 display. This is because there is no way of telling the LCD controller that there are only 32 characters on the attached display.

Here is a drawing of the complete memory map. Note that this drawing is the same as the one for the 20 x 2 display except that a different range of addresses on the right side are greyed out.

The operation of this display when a long string of characters is sent to it is that same as described for the 20 x 2 display except that there is a gap of 24 missing characters at the end of each line (instead of 20).

There are actually two different varieties of 16 x 1 LCD displays and the initialization and operation of each is different so it is important to determine which one you have.

When power is first applied to any of the multi-row LCD modules and before the controller is initialized you will see that the character locations corresponding to the first line of memory are dark and the others are light (assuming that the contrast adjustment is properly set). If you apply power to a 16 x 1 LCD module and only the left 8 character locations are dark you have what I will call a type 1 module. If only the right 8 character locations are dark this is also a type 1 module but it is upside down! If all 16 character locations are dark then it is what I will call a type 2 module. This is my own terminology used only for the purpose of keeping them differentiated while describing their operation. The type 1 modules will have only one IC on the back of the pcb while the type 2 will have 2 (I guess this tidbit gives away the source of my "type" designations). This distinction may apply to newer devices with epoxy blobs instead of ICs, but I believe that sometimes one blob may cover more than one equivalent IC function.

From this you can see that although the display has only a single row of characters, as far as the LCD controller is concerned it is using two lines of memory and it must be considered to be a 2 line device when initializing the controller.

Here is a drawing of the complete memory map. Note that this drawing is the same as the one for the 20 x 2 and 16 x 2 displays except that a different range of addresses on the right side are greyed out.

Here you can see that if the host controller sends a long string of characters without periodically adjusting the DDRAM starting address then after each 8 characters are displayed the next 32 will "disappear".

Also, to display a message of more than 8 characters on the 16 character display the host controller will have to readjust the DDRAM address after displaying the first 8 characters.

Here is a drawing of the complete memory map. Note that this memory map is different than all of the previous ones. This is the only device described here that is a true "one-line" display (see note 2) and as such it has a different memory map.

Here you can see that if the host controller sends a long string of characters after the first 16 characters are displayed the next 64 will "disappear".

At the expense of an extra IC you get some slightly easier programming since, in order to display a message of more than 8 characters on the 16 character display, the host microcontroller does not have to readjust the DDRAM address after displaying the first 8 characters.

Since only one line of memory is in use this LCD module should be configured as a 1-line device. As far as I can determine, this changes the multiplex frequency which changes the display brightness and/or contrast. Also, there are some single row LCDs that are capable of displaying a larger 5x10 font instead of the more common 5x7 font.

Here is the same memory map, rearranged this time to show how the memory addresses relate to the character positions on a 16 x 4 LCD. Note how the center of the previous diagram is now below the left part, the right part is missing, and the resulting sequence of starting addresses for each display row is different than for the 20 x 4 (00h, 40h, 10h, 50h).

Here you can see that if the host controller sends a long string of characters without periodically adjusting the DDRAM starting address then after the first row is full the characters will continue on to the third row. After the third row is full the next eight characters "disappear". The normal automatic incrementing from 27h to 40h will then cause the display to continue on the second row, and from there it will continue to the fourth row. After the fourth row is full the next eight characters will "disappear" and then it"s back to the first row.

The 40 x 4 LCD is treated essentially as two 40 x 2 devices stacked one on top of another in the same glass enclosure. Electrically it uses what amounts to two HD44780 controller chips and it therefore has two separate memory maps each with the same address range. One is used for the top two lines and the other is used for the bottom two lines. The memories are accessed individually by strobing the desired Enable pin of which there are now two. Here is a diagram of the device.

To display a really long string of characters on this display the host controller would start out just like it did for the 40 x 2 display. It would specify a starting DDRAM address (typically 00h) and then start sending the string of ASCII codes corresponding to the desired characters to the LCD controller, one after another, making sure to strobe the enable pin associated with the upper memory bank.   After storing an ASCII code in address 67h the LCD controller will automatically increment to address 00h as before and at this time the host controller must stop strobing the enable pin for the upper bank and start strobing the one for the lower bank.

There are other LCD configurations available but I believe that any of them can be handled by a technique similar to one of the examples above. If you have a display that seems to be considerably different from any of these I would like to hear from you.

(1) The mysterious gap is due to considerations resulting from the multiplexing of the display.   The DDRAM addressing uses seven bit addressing and the highest bit signifies which row of memory is involved.   If you compare the addresses in the first row with those just below in the second row you will see that the only difference is in that one bit.

(2) As implied above the number of rows of characters that can be displayed on the LCD is not the same as the number of lines of memory used by its controller.   Only some of the 16x1 displays use "one line" of memory, all of the other displays including most 16x1 displays, use "two lines" of memory.