BS2824 Holtek Semiconductor Inc., BS2824 Datasheet - Page 61

• Manufacturer Part Number: BS2824
• Description: Touch Key Mcu
• Manufacturer: Holtek Semiconductor Inc.

Rev. 1.00
6+2 PWM Mode
Each full PWM cycle, as it is controlled by an 8-bit PWM register, has 256 clock periods. However,
in the 6+2 PWM mode, each PWM cycle is subdivided into four individual sub-cycles known as
modulation cycle 0 ~ modulation cycle 3, denoted as i in the table. Each one of these four sub-cycles
contains 64 clock cycles. In this mode, a modulation frequency increase of four is achieved. The
8-bit PWM register value, which represents the overall duty cycle of the PWM waveform, is divided
into two groups. The first group which consists of bit2~bit7 is denoted here as the DC value. The
second group which consists of bit0~bit1 is known as the AC value. In the 6+2 PWM mode, the duty
cycle value of each of the four modulation sub-cycles is shown in the following table.
The following diagram illustrates the waveforms associated with the 6+2 mode of PWM operation.
It is important to note how the single PWM cycle is subdivided into 4 individual modulation cycles,
numbered from 0~3 and how the AC value is related to the PWM value.
Modulation cycle i
Parameter
(i=0~3)
PWM Register for 6+2 Mode
6+2 Mode Modulation Cycle Values
6+2 PWM Mode
61
BS2824/BS2854/BS2868
AC (0~3)
i<AC
i AC
DC (Duty Cycle)
Touch Key MCU
DC+1
DC
64
64
January 27, 2010