Ise Electronics Corp

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CL VFDs Application Note APN130

4. CONTROL PROCEDURE

4.1 Data Transfer Protocol

Figure 13 and 14 shows an example of data transfer protocol in the case of a CL VFD with 1x16 silicon chips(=256x16dot).

Fig.13 Data Transfer Timing Chart

Fig.14 Shift Register Map

Each bit in shift register is assigned to each dot on the silicon chip on one-on-one basis. The relevant assignment order is explained in "Dot assignment and shift register" or "Data sending order" on the individual specification.
Each dot is turned on/off by setting each related bit in shift register as "High" or "Low".
The silicon chip has the data latch control function, so the content of latched data is kept until it is latched again. For example, during this period if the data in shift register is "High", the related dot stays "ON" programmed differently.

4.2 Display Enable UPDATE

The silicon chip of the CL VFD has display on/off enable control function. By using the enable control, the (all) display can be turned on/off or made to blink, irrespective of the data set in shift register.

EN = High or OpenDisplay ON
EN = LowDisplay OFF

To avoid miss-transfer of data due to switching noise, do not change "EN" from "Low" to "High" or "High" to "Low" when setting data into shift register.

Fig.14b Enable Control Timing

4.3 Brightness Control

The brightness level (intensity of display screen) can be adjusted by the enable function.
When brightness is adjusted by using the enable function, the enable pulse needs to have a frequency of minimum 100Hz in order to avoid flickering the display. The following shows the brightness change when brightness is adjusted by the enable function.

Brightness = tEN/Tx100(%)

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