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BS67F340/BS67F350/BS67F360/BS67F370
Enhanced Touch A/D Flash MCU with LCD Driver
BS67F340/BS67F350/BS67F360/BS67F370
Enhanced Touch A/D Flash MCU with LCD Driver
Programming Considerations
Certain precautions must be taken when programming the LCD. One of these is to ensure that
the LCD Memory is properly initialised after the microcontroller is powered on. Like the General
Purpose Data Memory, the contents of the LCD Memory are in an unknown condition after power-on.
As the contents of the LCD Memory will be mapped into the actual display, it is important to
initialise this memory area into a known condition soon after applying power to obtain a proper
display pattern.
Consideration must also be given to the capacitive load of the actual LCD used in the application.
As the load presented to the microcontroller by LCD pixels can be generally modeled as mainly
capacitive in nature, it is important that this is not excessive, a point that is particularly true in the
case of the COM lines which may be connected to many LCD pixels. The accompanying diagram
depicts the equivalent circuit of the LCD.
One additional consideration that must be taken into account is what happens when the
microcontroller enters the IDLE or SLOW Mode. The LCDEN control bit in the LCDC0 register
permits the display to be powered off to reduce power consumption. If this bit is zero, the driving
signals to the display will cease, producing a blank display pattern but reducing any power
consumption associated with the LCD.
After Power-on, note that as the LCDEN bit will be cleared to zero, the display function will be
disabled.
LCD Panel Equivalent Circuit
Touch Key Function
Each device provides multiple touch key functions. The touch key function is fully integrated and
requires no external components, allowing touch key functions to be implemented by the simple
manipulation of internal registers.
Touch Key Structure
The touch keys are pin shared with the I/O pins, with the desired function chosen via the pin-shared
selection register bit. Keys are organised into several groups, with each group known as a module
and having a module number, M0 to Mn. Each module is a fully independent set of four Touch Keys
and each Touch Key has its own oscillator. Each module contains its own control logic circuits and
register set. Examination of the register names will reveal the module number it is referring to.