Basic Timer1 Introduction
11-5Basic Timer1
11.2.4 Basic Timer1 Operation: Signal fLCD
The LCD controller (but not the LCDA controller) uses the fLCD signal from the
BTCNT1 to generate the timing for common and segment lines. ACLK sources
BTCNT1 and is assumed to be 32768 Hz for generating fLCD. The fLCD
frequency is selected with the BTFRFQx bits and can by ACLK/256,
ACLK/128, ACLK/64, or ACLK/32. The proper fLCD frequency depends on the
LCDs frame frequency and the LCD multiplex rate and is calculated by:
fLCD = 2 × mux × fFrame
For example, to calculate fLCD for a 3-mux LCD, with a frame frequency of
30 - 100Hz:
fFrame (from LCD datasheet) = 30 - 100 Hz
fLCD = 2 × 3 × fFrame
fLCD(min) = 180 Hz
fLCD(max) = 600 Hz
select fLCD = 32768/128 = 256 Hz or 32768/64 = 512 Hz
The LCD_A controller does not use the Basic Timer1 for fLCD generation. See
the LCD Controller and LCD_A Controller chapters for more details on the LCD
controllers.
11.2.5 Basic Timer1 Interrupts
The Basic Timer1 uses two bits in the SFRs for interrupt control.
-Basic Timer1 interrupt flag, BTIFG, located in IFG2.7
-Basic Timer1 interrupt enable, BTIE, located in IE2.7
The BTIFG flag is set after the selected time interval and requests a Basic
Timer1 interrupt if the BTIE and the GIE bits are set. The BTIFG flag is reset
automatically when the interrupt is serviced, or can be reset with software.