Introduction

In systems with relatively small (monochrome) LCDs (quarter VGA or less), there is no need for an LCD controller. The microcontroller can do the job of the LCD-controller on the side, refreshing the display in an interrupt service routine. The memory of the controller is used as video memory. A generic configurable driver is available.

Advantages of this approach

• Very fast update of display possible
• Eliminating the LCD-controller (and its external RAM) reduces hardware costs
• Simplified hardware design
• 4 levels of gray or up to 64 colors can be displayed

How to connect the MCU to the row/column drivers

It is quite easy to connect the MCU to the row/column drivers. 5 control lines are needed, as well as either 4 or 8 data lines (depending on if the column drivers are able to operate in 8-bit mode). 8 bit mode is recommended as it is more efficient, saving calculation time of the CPU. All data lines should be on a single port, using port bits 0..3 or 0..7 in order to guarantee efficient access.

CPU load

The CPU load depends on the hardware and controller used, as well as on the size of the display.

Example:
Renesas M16C62 Controller , 16MHz, 160*100 display, 8 bit interface, 80 Hz Update
app. 12% CPU load
Renesas M16C62 Controller , 16MHz, 240*128 display, 8 bit interface, 80 Hz Update
app. 22% CPU load

More information

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