Intel 8XC251SA, 8XC251SP, 8XC251SQ, 8XC251SB manual Pulse Width Modulation Mode, PCA 8-bit PWM Mode

PROGRAMMABLE COUNTER ARRAY

9.3.6Pulse Width Modulation Mode

The five PCA comparator/capture modules can be independently programmed to function as pulse width modulators (Figure 9-5). The modulated output, which has a pulse width resolution of eight bits, is available at the CEXx pin. The PWM output can be used to convert digital data to an analog signal with simple external circuitry.

In this mode the value in the low byte of the PCA timer/counter (CL) is continuously compared with the value in the low byte of the compare/capture register (CCAPxL). When CL < CCAPxL, the output waveform (Figure 9-6) is low. When a match occurs (CL = CCAPxL), the output wave- form goes high and remains high until CL rolls over from FFH to 00H, ending the period. At roll- over the output returns to a low, the value in CCAPxH is loaded into CCAPxL, and a new period begins.

CCAPxH

CL rollover from FFH to 00H loads

CCAPxH contents into CCAPxL

X= Don't Care x = 0, 1, 2, 3, 4.

CL

8

CCAPxL

8

8-Bit

"0"

CL < CCAPxL

(8 Bits)

Comparator

Enable

CEXx

CL ≥ CCAPxL

"1"

X	ECOMx	0		0	0	0	PWMx	0
7			CCAPMx Mode Register					0

A4166-01

Figure 9-5. PCA 8-bit PWM Mode

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