VFD MODULE APPLICATION NOTE

CUSTOM VFD
MODULES


1	What is a Custom VFD Module
2	Construction
3	Power Supply
4	Communication Interfaces
5	Initialisation and Synchronisation
6	Software Commands
7	Character Fonts
8	Key Scan and User Input/Output
9	Front Panel Designs
10	Environmental Parameters
11	Custom Design Procedure
	Download Custom Request Form

The contents of this document are subject to copyright and may not be amended or included in other documents or media without the express permission of Noritake Co., Limited, Japan. Revised 12th August 2001.

1 What is a Custom VFD Module
> Optimum Functionality > Optimum Application Cost > Optimum Size	Noritake Itron supplies a wide range of standard modules designed to meet 50% of market requirements, however, optimising the available space and integrating specific functions will provide a cost effective solution through custom design. Noritake Itron provides a twin track custom service providing low quantity solutions from 500/yr through to high volume manufacture above 5000/yr. Customisation can be as simple as a connector or font modification through to a completely new design. Many custom modules include a key scan interface and bi-directional serial interface since this can be incorporated at little extra cost. The diagram below shows the functionality that is available. If you have any unique features, please do not hesitate to specify them.
Summary of Typical Options for Custom Modules

2 Construction
Side Views	The most cost effective method is to mount all the components on the same side of the printed circuit board (PCB) with no components under the display . This may be difficult where the area is not available or the profile of certain components is higher than the display.
	The VF display and other front panel through hole mounted components are mounted on one side of the PCB with the remaining surface mounted components on the other side. This makes the overall dimension a minimum in most solutions.
	The total surface mount construction enables a component free rear side to the PCB allowing easy mounting in an enclosure.
	The VFD can be reverse mounted and viewed through an aperture in a 2.4mm thick PCB with a front panel overlay integrating filter and dome keys secured to the PCB.

3 Power Supply
Most modules require a single 5VDC supply for a DC/DC converter to generate the AC filament voltage and grid/anode voltages required by the VF display and supply the CPU and associated logic. There are many exceptions in point of sale, amusement and transportation equipment where 10 to 36VDC may be required, with demand for higher efficiency and 3.3V operation in compact equipment. A fixed operating frequency may be required for the power supply to avoid interference with critical measurement sensors in the users product. New developments in power supply control and patents by Noritake in transformer-less designs seek to address many of these issues.
VFD and Logic Voltages		The user may provide all the necessary voltage levels from a suitable power supply in their equipment. The parameters should be decided in consultation with the VFD glass specification and application notes. Please consider voltage regulation tolerances.
5VDC		Most 5V modules use a DC/DC converter circuit incorporating a transformer to supply the VFD voltages and logic supply. Dimensional height as low as 3mm is possible. Ultra low profile applications can use a transformer-less design where the VFD specified is suitable (filament voltage less than 4.5V).
12VDC		The majority of VFDs are easily powered from 12VDC with the possibility of 20% tolerance where required. An on board regulator supplies logic circuit requirements.
3.3VDC		The Noritake Itron CIG (Chip in Glass) VFD can be specified for 3.3V operation and many micro-controllers and ASIC processes are now available at this voltage. In many applications where the 3.3V supply is obtained via a DC/DC converter, it is best to generate the VFD filament and anode/grid voltages from the source supply.
10 to 36VDC		Many transportation applications demand a wide operating voltage range due to the battery supply of the vehicle or system. A transformer or inductor switching circuit can accommodate this request.
Other Voltages		Specific requests will be considered.
Power Save / Sleep Mode		This function can be successfully implemented where the power supply is controlled by a slow start regulator or is a transformer-less type. This is required in order to prevent the CPU reset circuit being triggered by a current surge.
Power Supply Connector		Please consider the current rating of the connector and the durability according to how often it will be inserted and removed and the operating environment. The power supply connection can be combined with the signal connection, but the wires should be suitably isolated to prevent induced noise and current surges causing incorrect operation.

4 Communication Interfaces

The following table lists many popular interfaces used by host systems with their key attributes.

INTERFACE	Type	Key Signal Connections	Cable Length	Bit Rate	Good Features
Synchronous Serial	SPI	Clock, Sin, Sout, /SS	< 2m	< 500k	Minimum Ports
Synchronous Serial	I²C	Clock, Bi Directional Data	< 1m	< 1M	Minimum Ports
Asynchronous Serial	TTL / CMOS	SIN, SOUT	< 1m	< 250k	Lowest Cost
	RS232C	RXD, TXD, DTR, CTS	< 30m	< 115k	Compatibility
	RS485	A, B	< 1000m	< 115k	Long distance
	USB	A, B	< 2m	< 2M	PC interface
Parallel	M68 BUS	E, R/W, RS, D0-D7, CS	< 0.5m	< 32M	High Speed
	i80 BUS	/WR, /RD, A0, D0-D7, /CS	< 0.5m	< 32M	High Speed
	PORT	STROBE, BUSY, D0-D7, /CS	< 2m	< 8M	Simple

4.1 Selecting an Interface

If the required interface is not defined by that available on the host system, please select an interface based on cable length, data transfer rate and the number of inter-connection lines available.

Parallel Interfaces
ASIC controllers with parallel interfaces are available for use with conventional and CIG VFD. They are used in many Noritake Itron GU and CU-U series standard products. The high data rate and short busy period makes an ASIC ideal for efficient processing and fast image update on graphic displays. The data setup and hold times for the CPU and ASIC must be evaluated for compatibility. Additional logic can be provided to resolve differences. It is helpfull to know the type of CPU used in the host system and it's operating speed.

Serial Interfaces
The data transfer rate for dot graphic displays can make serial interfacing at low speed (less than 19200 bits per second) impractical for bit image processing due to the time taken to fill the screen with data. Storing fonts and images in the display controller and utilising a high level command set can resolve this problem.

4.2 Interface Connectors

Connection method depends on the proximity of the host, insertion and removal life time, the environment and isolation requirements. The standard 2.54mm pitch IDC connector is popular with miniature versions now being used. Compact equipments use flexible circuit interconnection where a one-time insertion is required. Interleaving the data signals with ground lines can reduce cross talk but will require a larger connector.

5 Initialisation and Synchronisation

Stable operation of the module will depend on correct power-on reset, initialisation and synchronisation with the host system. In the event of induced noise or interference, a strategy must be employed to ensure the module continues to function within the parameters required by EMC legislation.

It is recommended that the module has an external reset input connected to the host and uses an internal watchdog circuit which may be triggered by a software error or power supply interruption. Additionally, the module should have a means of communicating it's status to the host system through bi-directional communication or a status output.
Cost and compatibility constraints may make these ideals un-achievable, so a compromise solution is adopted.

Users must investigate and deploy a strategy appropriate to their application, so, we will work together to resolve the issues which affect the display module. Strategies include the use of Checksums, Dual Pulse Width Reset Inputs, Voltage Brown Out Detection, Hardware and Firmware Watchdogs, Error Detection and Parity.

6 Software Control Commands

Standard ASIC controllers will have a defined command set which provides the basic functionality required for the module. A programmable micro-controller offers the option to integrate commands specific to the functionality of your application which can free up host system processing time. Control of the hardware in your custom module will define many of the commands but it is possible to develop a high level language to provide interactive messaging on character modules through to line and circle drawing on graphics modules.
The following table show many examples from which you can select or adapt for your application.

Display Appearance	Display On
	Display Off with power down if the hardware exists, the existing memory data is unchanged.
	Set Display Brightness
	Merge RAM Areas on the Display using logical OR / AND / EXOR for graphic images.
Display Fonts	Set Active Character / Icon / Graphic Font
Display Fonts	Load User Font by sending the character code followed by several bytes of dot data
Display Data	Write Data to Cursor Position
Display Data	Read Data at Cursor position
Display Clear	Clear Display . Cursor moves to top left position of display.
	Clear Current Cursor Line and move cursor to left end of line.
	Clear to End of Line from current cursor position
Display Set	Start Self Test Routine to show fonts or default message if exists.
Display Set	Write Default Message and Timeout to EEPROM if hardware exists
Flashing Characters	Written Character will Flash
Flashing Characters	Written Character will not Flash
Scroll Display	Display Scrolls Up from Cursor Line
	Display Scrolls Down from Cursor Line
	Display Line Scrolls Left from Cursor Position
	Display Line Scrolls Right from Cursor Position
Cursor Appearance	Set Cursor as Underline. Position defined by font.
	Set Cursor as Block. Size defined by font.
	Set Cursor Flashing. If block, alternates with back ground character.
	Cursor Off. Also resets appearance to non flashing underline.
Auto Move Cursor	Set Cursor Active Area as limit of movement.
	Set Cursor Auto Increment after Write/Read. Stops at end of line.
	Set Cursor Auto Decrement after Write/Read. Stops at start of line.
	Set Cursor to remain Static after Write/Read
Cursor Position	Move Cursor to Top Left Position (Home)
	Move Cursor to Start of Current Line (Carriage Return)
	Move Cursor Up a Line (Vertical Tab)
	Move Cursor Down a Line (Line Feed)
	Move Cursor Left unless start of line (Back Space)
	Move Cursor Right unless end of Line (Horizontal Tab)
	Position Cursor (A)bsolute or X,Y if more than 256 positions.
	Read Cursor Position. Format same as Position Cursor.
Asynchronous Serial (RS232/RS485)	Set Asynchronous Serial baud rate, parity, checksum and protocol
	Read Asynchronous Serial byte
	Write Asynchronous Serial byte
Synchronous Serial (SPI)	Set Synchronous Serial Protocol and clock rate if hardware permits.
	Write Synchronous Serial Byte
	Read Synchronous Serial Byte
User I/O Ports	Set user port bits to input or output (At power on reset, all are generally inputs)
	Set user port inputs as triggered active low.
	Set user port inputs and outputs as key matrix
	Write to user port outputs (inputs are automatically avoided)
	Read user port inputs and outputs
Multi-drop Addressing	Read Multi-drop Address from port setting and set multi-drop addressing as active.
Multi-drop Addressing	Set New Active Address for communication.
Other	Extended command functions can use a command byte like ESCape
	Software Reset requests the module to set all internal registers and ports to that at power on.
	Enable Busy to activate every second to act as a Watchdog
	Enable Keyboard / Serial / User Port Interrupt Requests
	Interrupt Response provides a defined output or communication when and interrupt occurs.
	Read Status Check Byte for Busy / Reset condition in the module.
	Read RAM / Register Checksum test is performed and sent to the host.

7 Character Fonts

Character fonts are included in modules to enable reduced data transfer between the host system and module. Although every application has it's specific requirements, some common character sets exist which have established industry standards. The ASCII character set (American Standard Code for Information Interchange) was developed for compatibility between equipment and is probably a subset of nearly all sets. Demands for Japanese Katakana and European fonts has evolved the two sets shown below for 5x7 fonts. These can be shown in horizontal or vertical orientation of alphabet sequence depending on user choice.

   ASCII + Katakana Font


ASCII + European Font

When the module control circuit includes a programmable ROM either internally within the micro-controller or as a separate integrated circuit, the user can define any combination of character patterns. You can save the bitmap images shown above to a new file and update the pixels in a bit map editor like Paint, then re-submit them for inclusion in your product. Alternative fonts are available on the website or by emailing a request.

Additionally, the module may accommodate user defined characters which can be written in dot form by the host and later displayed by sending the appropriate character data. This function will need to be considered as a software command.

8 Key Scan and User Input / Output
	Key Scan - Special Techniques Since the proximity of the key board is generally close to the display and many micro-controllers have extra I/O ports, it is common to include the key scan task as a function of the custom display module at minimal extra cost. A connector can be included on the module to accept a flexi-tail from a keyboard or the key switches can be incorporated into the module. Any combination of XxY key board matrix can be handled, with 10 to 30 keys meeting the requirements of many applications. We have developed special scan techniques to avoid the use of cross-over diodes and enable 'on the fly' shift keys with auto repeat and de-bounce with resistive touch panels.
	User I/O - Multiple Options Many applications use light emitting diodes for additional status indication, with some placed behind the keys. The control of other inputs and outputs from infra-red and A/D converters to relays and expansion interfaces for printer drive is possible.

9 Front Panel Designs

A front panel assembly is supplied ready to fit inside the users product. It can consist a multi-coloured printed polymer overlay incorporating filter and
embossed key pads secured to an aluminum sheet with mounting holes and studs.

A cable assembly fitted to the VFD module on the back and individual packing allows the product to be easily loaded on the production line, assembled and tested.

Users can supply their front panel overlay request as a picture or drawing file.

10 Environmental Conditions
Temperature and Humidity		The development of CIG VFD has enabled an operating temperature range of -40C to +85C. The module operating range is dependent on the other components which may offer cost advantage when specified at -20C to +70C or 0C to +50C. Please consider and specify the minimum operating range. Although VFD modules offer a wide operating humidity compared to other display technologies, please define your application and requirement.
Shock and Vibration		VFDs are widely used in transportation and industrial equipment where significant vibration and shock is present. Please specify the level of immunity required for your application since this will impact on the construction of the module.
EMC		Electro Magnetic Compatibility legislation requires electrical and electronic equipment to meet certain criterion for susceptibility to and emission of interference. We work with our customers to design products which assist them in meeting these requirements through applying good design rules and suitable component solutions. The equipment enclosure and the screening of it's apertures are critical factors in any design so please discuss the options with us.

11 Custom Design Procedure
Submit Request		Please download a request form, enter information as appropriate and fax it to the nearest Noritake Itron office with any additional information you can provide.
Evaluation		We will confirm receipt and evaluate the request. Our local representative office may contact you to clarify certain aspects of the design.
Quotation		The initial quotation we supply will be subject to approval of specification. We may suggest alternate design options to seek to optimise the application cost.
Specification		If the initial quotation is acceptable, we will prepare a specification for signature. Any alterations to the specification will be subject to re-quotation.
Development Order		Please supply a development order to instruct us to proceed with the design. The order should specify the number of prototypes you require for evaluation and approval. Review of the design on completion of circuit, PCB layout and software stages is undertaken to ensure compliance. Any deviations will be communicated to the you and we request any changes in your design be communicated to us immediately. We will assess their impact and advise.
Sample Evaluation		We will submit the prototypes for evaluation and approval.
Approval		A confirmation of approval is required in writing from an authorised person in your organisation prior to commencement of component ordering or manufacturing.
Manufacturing Order		If the timescale for manufacture requires material to be purchased in advance of approval, our quotation will specify the terms and conditions that apply. Please communicate your order forecast on a rolling basis.