Texas Instruments MSC1210 4. Configuring the PWM for Tone Generation with PWM Idling, Explanation

PWM Generator

Table 11−4. Configuring the PWM for Tone Generation with PWM Idling

Stmt	‘C’ Source Code	Assembly Source Code
1	// PWM	PUBLIC main
		RSEG ???main?PWM
2	#include <reg1210.h>
3	#define OneUsConst (2−1)
4	sbit p33=p3^3;
5	void main(void)	Main:
6	{
7	PDCON &= 0xED; // turn on tone gen & sys timer	ANL PDCON,#0Edh
8	USEC = OneUsConst;	MOV USEC,#01h
9	P33 = 1; // turn on P3.3	SETB p33
10	PWMCON = 0; // select PWMPeriod	MOV PWMCON,#00h
11	PWM = 5; // Set PWMPeriod	MOV PWMHI,#00h
		MOV PWMLOW,#05h
12	PWMCON = 0x10; // select PWMDuty	MOV PWMCON,#10h
13	PWM = 0; // Set PWMDuty	MOV PWMHI,#00h
		MOV PWMLOW,#04h
14	PWMCON = 0x09; // Enable PWM	MOV PWMCON,#09h
15	for(i=0; i < 10; i++);	MOV R7,#00h
		Loop:
		INC R7
		CJNE R7,#0Ah,Loop
16	PWMCON = 0x10; // select PWMDuty	MOV PWMCON,#10h
17	PWM = 4; // Set PWMDuty	MOV PWMHI,#00h
		MOV PWMLOW,#04h
18	PWMCON = 0x09; // Enable PWM	MOV PWMCON,#09h
19	while(1) {}	SJMP $
20	}

Table 11−5. Statement Explanations

Statement #	Explanation
1−12	Same as previous program in section 11.3.1.
13	Sets PWM Duty to 0, thereby configuring the PWM tone generator for idle mode.
14	Enables PWM. The PWM is enabled, but is in idle mode due to the fact that PWM Duty is 0.
15	This loops for an arbitrary number of instructions.
16−20	Same as statements 12 to 16 in previous program in section 11.3.2.

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