Fujitsu F202RA, MB89202 manual Program Example of PWM Timer Functions, 159

CHAPTER 7 8-BIT PWM TIMER

■Program Example of PWM Timer Functions

●Processing specifications

•A PWM wave with a duty ratio of 50% is generated. The duty ratio is then changed to 25%.

•No interrupt occurs.

•When the count clock is 16 tINST of an internal count clock, the cycle of the PWM wave is 16 ⋅ 4/12.5 MHz ⋅ 256 = 1.3107 ms, which occurs when the top speed of the gear (one instruction cycle = 4/FCH) is

obtained at an oscillation frequency of 12.5 MHz.

•The COMR register value with a duty ratio of 50% is shown below. COMR register value = 50/100 ⋅ 256 = 128 (080H)

●Coding example

CNTR	EQU	0022H	; Address of the PWM control register
COMR	EQU	0023H	; Address of the PWM compare register
TPE	EQU	CNTR:3	; Defining the bit to enable the counter operation
;------------------------		Main program---------------------------------------------------------------------------------
	CSEG		; [CODE SEGMENT]
	:
	CLRB	TPE	; Stopping the counter operation
	MOV	COMR,#80H	; Specification of the H-level width of a pulse, 50% duty
			ratio
	MOV	CNTR,#10011010B	; PWM timer operation, selection of 16 tINST
			; Starting the counter operation, clearing the interrupt
			request flag
			; Enabling the output of the PWM pin, disabling the output
			of interrupt requests
	:
	:
	MOV	COMR,#40H	; Changing the duty ratio to 25% (Takes effect at the next
			cycle of the PWM wave.)
	:
	ENDS
;---------------------------------------------------------------------------------------------------------------------
	END

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