Motorola MC68HC05T16 Technical Data Manual page 70

In order to prevent transient noise at the output during MCU write to the 8-bit PWM and 6-bit BRM
registers, double buffering is used. Programming of the 2 registers must follow the sequence as
shown below:
LDA BRM_value
STA $35
LDA PWM_value
STA $36
The instruction STA $35 simply puts the 6-bit BRM data in a buffer. Output is not affected at this
time. The instruction STA $36, then, puts the total 14-bit data to BRM and PWM register at the
same time. Output waveform will change accordingly starting from the beginning of the next PWM
cycle.
8
MOTOROLA
8-4
;Data put in 6-bit BRM buffer
;Load 6-bit BRM and 8-bit PWM register
PULSE WIDTH MODULATOR
TPG
MC68HC05T16