9202 datasheet(73/175 Pages) STMICROELECTRONICS

73 / 175 page

73/175

UPSD3254A, UPSD3254BV, UPSD3253B, UPSD3253BV

PULSE WIDTH MODULATION (PWM)

The PWM block has the following features:

Four-channel, 8-bit PWM unit with 16-bit

prescaler

One-channel, 8-bit unit with programmable

frequency and pulse width

PWM Output with programmable polarity

4-channel PWM Unit (PWM 0-3)

The 8-bit counter of a PWM counts module 256

(i.e., from 0 to 255, inclusive). The value held in

the 8-bit counter is compared to the contents of the

Special Function Register (PWM 0-3) of the corre-

sponding PWM. The polarity of the PWM outputs

is programmable and selected by the PWML Bit in

PWMCON register. Provided the contents of a

PWM 0-3 register is greater than the counter val-

ue, the corresponding PWM output is set HIGH

(with PWML = 0). When the contents of this regis-

ter is less than or equal to the counter value, the

corresponding PWM output is set LOW (with

PWML = 0). The pulse-width-ratio is therefore de-

fined by the contents of the corresponding Special

Function Register (PWM 0-3) of a PWM. By load-

ing the corresponding Special Function Register

(PWM 0-3) with either 00H or FFH, the PWM out-

put can be retained at a constant HIGH or LOW

level respectively (with PWML = 0).

For each PWM unit, there is a 16-bit Prescaler that

are used to divide the main system clock to form

the input clock for the corresponding PWM unit.

This prescaler is used to define the desired repeti-

tion rate for the PWM unit. SFR registers B1h -

B2h are used to hold the 16-bit divisor values.

The repetition frequency of the PWM output is giv-

en by:

fPWM8 = (fOSC / prescaler0) / (2 x 256)

And the input clock frequency to the PWM

counters is = fOSC / 2 / (prescaler data value + 1)

See the I/O PORTS (MCU Module), page 47 for

more information on how to configure the Port 4

pin as PWM output.

9202 数据表(PDF) 73 Page - STMicroelectronics

9202 数据表(HTML) 73 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载