Intel 80C196NU, Microcontroller manual PWM Functional Overview, PWM Block Diagram 8XC196NP Only

CHAPTER 9

PULSE-WIDTH MODULATOR

The pulse-width modulator (PWM) module has three output pins, each of which can output a PWM signal with a fixed frequency and a variable duty cycle. These outputs can be used to drive motors that require an unfiltered PWM waveform for optimal efficiency, or they can be filtered to produce a smooth analog signal.

This chapter provides a functional overview of the pulse-width modulator module, describes how to program it, and provides sample circuitry for converting the PWM outputs to analog signals. For detailed descriptions of the signals and registers discussed in this chapter, please refer to Ap- pendix B, “Signal Descriptions” and Appendix C, “Registers.”

9.1PWM FUNCTIONAL OVERVIEW

The PWM module has three channels, each of which consists of a control register (PWMx_CONTROL, where x is 0, 1, or 2), a buffer, a comparator, an RS flip-flop, and an output pin. Two other components, an eight-bit counter and a clock prescaler, are shared across the PWM module’s three channels, completing the circuitry (see Figures 9-1 and 9-2).

	8
		PWMx_CONTROL	Load
		8	Buffer
		Bufferx
		8
CON_REG0.0		Comparatorx	=
			RS Flip-flopx
	(CLK0 Bit)				Port 4
			R
					Control
	Prescaler	8		Q	P4_MODE
		0
			S	PWMx	P4.x/
Internal		Up Counter		Output	PWMx
Clock	– 2	1	Overflow
Signal		Shared Circuitry
					A2382-03

Figure 9-1. PWM Block Diagram (8XC196NP Only)

9-1