SELECTING A VFD
 MODULE FOR YOUR
 APPLICATION

1   Selecting a Module

2   Module Construction
3   Power Supply Requirements
4   Communication Interfaces
5   Module Reset
6   Software Commands
7   Character Sets
8   Design Precautions
9   Trouble Shooting
  Service & Warranty
   Custom Design Modules 

        

1 Selecting a Module View Module Function Comparison Table
A VFD module offers a fast and affordable development path and production solution for projects both large and small. 20 years experience and continuous research into new techniques allow us to provide you with a product which has been designed and manufactured to meet the ever demanding performance of today's applications.

Please determine the factors required for your application prior to making your selection. Cost critical applications may benefit from customizing a high volume standard solution. Please inquire.

Although many modules are now available with a combination of interfaces, additional interface modules are available in the MCB range to meet other requirements.

The vivid illumination of a VFD means that you can use a smaller character height compared to other technologies. Please view the table for an indication of viewing distance vs. height. We will now review the other factors shown in the table.
 
Factor VFD Options
Viewing Distance
Up to 1 metre
Up to 2 metres
 Up to 3 metres
 Up to 8 meters

Character Height / Dot Size
 2-4mm          0.3-0.4mm
 5-6mm          0.5-0.7mm
8-12mm        0.8-1.1mm
15-25mm          1.5-3mm 

Available Space

Dimension X, Y, Z

Available Power

5V, 12V or other.

Communication High Speed
Low Pin Out
Long Lead Length

Interface
8 bit Parallel
Serial
RS232/RS485 Serial

Software
ASIC Control
CPU Control
Low Level or High Level
Short Busy time (2us)
High Functionality
Display Font
5x7 ASCII
16x16 or Icons

Character     Graphic Module Yes                   Yes
No                     Yes

2 Module Construction
A VFD module typically includes a VFD glass, driver ICs, CPU or ASIC controller, a DC/DC converter and interface connection mounted on a printed circuit board (PCB). Mounting holes are provided at the four corners of the PCB with sufficient clearance for a spacing pillar. The VFD glass is secured to the PCB with pin connections soldered to the PCB. The VFD glass typically has an evacuation pipe extending 6 to 8 mm from the side, but normally this remains within the bounds of the PCB. Although most of the components are surface mouted with a profile less than 2mm, transformers, electrolytic capacitors and connectors will extend 5 to 10 mm from the PCB. Transformer-less modules have been designed to meet the requirement for low profile compact applications. Many modules are designed for IDC connection which are either supplied fitted or allow the user to specify their requirement.

       
3 Power Supply Requirements
Most modules operate from a single 5VDC supply. The exceptions are for specific applications in point of sale and amusement equipment where 12VDC is the typical supply voltage. Custom modules have been designed with wide operating capability of 10 to 36VDC for transportation applications.
It is important that the power source has a fast rise time and can supply the in rush current  where a transformer is used in the DC/DC converter. This can  be  twice the nominal operating current. Recent designs use a power supply control IC with fixed frequency and soft start. Transformer-less modules have the advantage of being able to start irrespective of how slow the rise time. Particular care should be taken when the module has a separate supply from the host due current flow in the signal/data lines causing incorrect initialisation.
        
4 Communication Interfaces
The following table lists many popular interfaces used by host systems with their key attributes. 
A common 0V ground connection is required between host and module except for USB and RS485.
INTERFACE TYPE KEY SIGNAL CONNECTIONS CABLE BIT RATE CHARACTER GRAPHIC

Synchronous
Serial

Clock Serial Clock, Sin, Reset, (C/D) < 1.3m <1MHz AU, CUx-T2/V GU-8, -K6xx

SPI

Clock, Sin, Sout, /SS, Reset

< 2m < 1MHz CUx-V -K6xx

IC

Clock, Bi Directional Data

< 1m < 1MHz  Custom Custom

Asynchronous
Serial

TTL / CMOS

SIN, SOUT

< 1m

< 250kHz CUx-T, -V -K610, 3000

RS232C

RXD, TXD, DTR, CTS

< 30m

< 115kHz CUx-V -K612, 3000

RS485

A, B

< 1000m

< 115kHz Custom -K611

USB

A, B

< 2m

< 2MHz  Custom GU-3x01
Parallel 

M68 BUS

E, R/W, Rs, D0-D7

< 0.5m

< 32MHz CUx-U GU-3xx/8xx

i80 BUS

/WR, /RD, A0, D0-D7

< 0.5m

< 32MHz CUx-U GU-3xx/8xx

PORT

STROBE, BUSY, D0-D7

< 2m

< 8MHz CUx-T Custom
     
4.1 Synchronous Serial Interfaces
A clock signal output by the host system provides a synchronizing reference for communicating data bits on a separate data input/output. The data should be stable on either rising edge or falling edge of the clock waveform depending on the system protocol. Since synchronous communication can easily be corrupted by noise, a reset signal is used prior to critical events to ensure both host and module are co-ordinated.

A 'clock serial' interface is the simplest method with single direction 'send' data to module. An additional signal line C/D may be used for command and data register selection.
The SPI interface is similar to clock serial, except a 'receive' data line 'Sout' and a device select line '/SS' can be used to select the module.

The IC interface uses a bi-directional data line and a software address protocol to select a module. 

   

4.2 Asynchronous Serial Interfaces
Communication is achieved by initiating a change of state in the data signal (start bit) followed by 8 fixed frequency periods (baud rate) for the synchronized transmission of data. This enables a 2 wire solution for many applications with inherent re-synchronization after each 8 bit data byte.

Transmission between host and module can be made at CMOS/TTL logic voltage levels over distances up to 0.5 metre. The idle state is logic high with data rates upto 115K bits per second.
Greater distance is achieved using RS232 voltage levels (+/-12volts) or a differential system like RS485 which uses two signal wires where the logic level is dependent on the polarity of the wires.  

After each data byte, a period is required to allow the module time to process the received data. A hardware control line can be used to indicate to the host that the module is busy. In certain modules an XOFF (13H) character is transmitted to the host to indicate the receive buffer is full. When ready, the module sends the character XON (11H).
 

   
4.3 Parallel Interfaces
The conventional CPU distributed data method uses a parallel 8 bit data bus. Two bus configurations evolved to provide data transfer control which are known as M68 bus and i80 bus. 
The M68 bus has an (E)nable clock signal and a direction control signal (R/W).
The i80 bus has a separate (/WR) signal for controlling the sending of data and (/RD) for receiving data.
Many modules allow either data bus to be connected by configuring a jumper link on the module PCB.

Additionally, one of the CPU address lines (A0 through to A15) can be used to select different data registers inside the module via the Rs, C/D or A0 input. This allows many additional display functions to be performed with a single command byte. 

When several peripheral devices connect to the same data and control bus, a chip select signal (/CS or CS) 

  
4.4 Other Interfaces
Wireless, Ethernet and Optical interfaces have evolved for messaging applications. Interface modules are available in the market to convert these interfaces to RS232.

5 Module Reset

Power On Reset
When power is applied to the display module, an internal reset circuit ensures the internal micro-controller or ASIC initializes correctly. The host system should allow at least 100ms before sending data to the module.  
Hardware Reset
Modules with a hardware reset allow the host system to restart the initialization sequence to ensure system integrity. The specification will define the period which should be allowed before data is transmitted.
     
6 Software Commands
The extent of the software commands in a module will determine it's flexibility to show data efficiently.
Cost constraints can restrict the commands available.
6.1 Character Display Commands
  T Series -  Standard ASCII    U Series - LCD Compatible

Instruction

D0-D7

Instruction

D0-D7

Back Space

08H

Katakana Font

19H

Horizontal Tab

09H

Escape

1BH

Line Feed

0AH

+Send User Font

+43H

Form Feed

0CH

+ Position cursor

+48H

Carriage Return

0DH

+ Software Reset

+49H

Clear Display

0EH

+ Luminance

+4CH

Increment Write Mode

11H

+ Flickerless Write

+53H

Vertical Scroll Mode

12H

+ Cursor Blink Speed

+54H

5x7 Block Cursor On

15H

Character Data

20H+

Cursor Off

16H

User Character Data

00H+

International Font

18H

 

 

Instruction

R/W

RS

D0-D7

 

Clear Display

L

L

01H

 

Cursor Return Home

L

L

02H-03H

 

Entry Mode Set

L

L

04H-07H

 

Display ON/OFF

L

L

08H-0FH

 

Cursor/Display Shift

L

L

10H-1FH

 

Function Set

L

L

20H-3FH

 

Brightness Set

L

H

00H-03H

 

Set CG RAM Addr.

L

L

40H-7FH

 

Set DD RAM Addr.

L

L

80H-E7H

 

Read BUSY/Addr.

H

L

00H-FFH

 

Write Data to RAM

L

H

00H-FFH

 

Read Data from RAM

H

H

00H-FFH

 

     
6.2 Graphic Display Commands
 GU-K6xxx4 Series

Command

Hex

Run Macro

01-07

Backspace

08

Horizontal Tab

09

Line Feed

0A

Home

0B

Vertical Tab

0C

Carriage Return

0D

Clear End of Line

0E

Test

0F

Cursor Position

10 + x + y

Set Area

11 +xl+yt+xr+yb

Clear Area

12 +xl+yt+xr+yb

Invert Area

13 +xl+yt+xr+yb

Set Outline

14 +xl+yt+xr+yb

Clear Outline

15 +xl+yt+xr+yb

Set Pixel

16

Clear Pixel

17

Graphic Write

18 + len + data

Reset

19

Write Mode - direction

1A + data

Set Macro

1B + macro+len+data

Erase All Macros

1B + 4D

Lock/Unlock EEPROM

1B + 4C/55

Request Checksum

1B + 43

Power On/Off

1B + 50/46

Enable/Disable Hex WR

1B + 48/42

Set Comms

1B + 49 + data

Enable I/O Port

1B + 44 + data

Set Port Lines

1B + 4F + data

Read Port

1B + 52

Enable key scanning

1B + 4B

Brightness

1B + F8-FF

Select Font

1C / 1D / 1E

Graphic Area Write*1

1F +xl+yt+xr+yb+data

Character Write

20 - FF

    GU-3000 Series

Command Name

Hex

Back Space

08

Horizontal Tab

09

Line Feed

0A

Cursor Home*

0B

Clear Display

0C

Carriage Return

0D

Escape

1B +

Specify Download Char

+25

Download Char. Definition

+26

Delete Download Char

+3F

Initialize Display

+40

Define International Font

+52

Define Char. Code Type

+74

Overwrite Mode

1F 01

Vertical Scroll Mode

1F 02

Horizontal Scroll Mode

1F 03

Cursor Set

1F 24

RAM Macro Processing

1F 3A

Display Brightness

1F 58

Macro Execution

1F 5E

Enable/Disable Reverse Dis

1F 72

Horizontal Scroll Speed

1F 73

Write Mixture Display Mode

1F 77

Dot Pattern Draw

1F 28 64

User Set Up Mode Start

1F 28 65

I/O Port Control

1F 28 70

Character Write

20 - FF

  GU-7000 Series

Command

Code

Character Write

20H-FFH

BS,HT,LF,CR,Display Clear

08H, 09H, 0AH, 0DH, 0CH

Initialize Display

1BH 40H

Specify International Font

1BH 52H n

Vertical Scroll Mode

1FH 02H

Horizontal Scroll Mode

1FH 03H

Cursor Set

1FH 24H xL xH yL yH

Scroll Display Action

1FH 28H 61H 10H wL wH cL cH s

Display Blank

1FH 28H 61H 11H p t1 t2 c

Screen Saver

1FH 28H 61H 40H p

Bit Image Display Group

1FH 28H 66H 11H xL xH

Font Magnified Display

1FH 28H 67H 40H x y

Brightness Level Setting

1FH 58H n

  GU-800 Series

Instruction

Instruction Byte

Set Display On/Off / Layer Merge

20H- 2FH

Set Display Brightness

40H-4FH

Clear Display

52H-5FH

Set Cursor XY Address

60H-67H

Set Display Start X Address

70H-7FH

Set Write Address Mode

80H-8FH

Scroll Display Vertically Up/Down

B0H-BFH

Read Cursor XY Address

D4H-D7H

Write Data

00H-FFH


 

   
7 Character Sets  
The module specification will define the included fonts in a matrix table having the high and low order hexadecimal nibbles on the axis. Capital 'A' = 40 + 01 = 41Hex

ASCII 
Standard upper and lower case alphabet and numeric characters are defined by the American Standard Code for Information Interchange (ASCII) and have character codes between 20Hex and 7FHex. Maintaining the same code for all equipments ensures that most text messages will be interpreted correctly. The symbolic characters are often modified to suit design requirements.
European 
These European characters extend local country requirements.
Katakana 
Katakana allows the phonetic representation of spoken Japanese words. This is used in 5x7 dot character displays where the display resolution or memory capability is limited.
Other Fonts
The remaining codes are often filled with a range of scientific or potentially useful fonts.
    

Font Table in the CU - U Series

Variable Sized Characters
Graphic displays offer the capability to enhance important information in a larger format. This can be achieved by selecting a larger font, scaling the existing font or down loading a user defined graphic image where the appropriate commands permit.
User Defined and Additional Fonts
Many modules provide internal RAM or EEPROM for the user to upload fonts or graphic icons specific to their application. A typical 5x7 character requires 5 data bytes of 8 bits to define the dot pattern. When a bit is set to '1' the related dot will illuminate. The module specification will have a dot assignment table indicating to which bits of the 5 bytes the dots are assigned. The following links provide a arrange of fonts for various micro-controllers which the user can cut and paste into their application software.  Hyperlinks:   8051    AVR     PIC16C62     H8    

      

8 Precautions
8.1 Design
Electrical - Power supply voltage operates at the typical level.
Connection - Keep cable lengths as short as possible
Mounting - Low mechanical stress applied to PCB.
8.2 Handling
Anti-Static Handling - Do not touch the module without anti-static precautions being taken.
Assembling - Do not apply undue stress to the module while fixing or connecting.
Connection with Power Off - Do not connect or disconnect the data cable or the power supply when ON.
      
9 Trouble Shooting
9.1 No Illumination
Blown Fuse CP1/FS1 - Reverse or intermittent connection of PSU.
VFD Glass Broken - Loss of vacuum causing the getter on the face glass to turn white.
Initialization - Incorrect or corrupted command sequence.
PSU - Insufficient current capacity in power supply.
Damage -  PCB or Interface.
9.2 Missing or Incorrect Characters
Interface - Miss match in timing or logic threshold levels.
Noise - Induced false trigger of clock or enable signal.
VFD Driver - Short circuit to VFD lead pin or drive IC failure