AT89LP2052 datasheet(26/90 Pages) ATMEL

26 / 90 page

3547F–MICRO–6/06

AT89LP2052/LP4052

15.5

Pulse Width Modulation

Timer 0 and Timer 1 may be independently configured as 8-bit asymmetrical pulse width modu-

lators (PWM) by setting the PWM0EN or PWM1EN bits in TCONB, respectively. In PWM Mode

the generated waveform is output on the timer's pin, T0 or T1. C/T must be set to “0” when in

PWM mode. In Timer 0's PWM mode, TH0 acts as an 8-bit counter while RH0 stores the 8-bit

compare value. When TH0 is 00H the PWM output is set high. When the TH0 count reaches the

value stored in RH0 the PWM output is set low. Therefore, the pulse width is proportional to the

value in RH0. To prevent glitches writes to RH0 only take effect on the FFH to 00H overflow of

TH0. Timer 1 has the same behavior using TH1 and RH1. See Figure 15-5 for PWM waveform

example. Setting RH0 to 00H will keep the PWM output low.

The PWM will only function if the timer is in Mode 0 or Mode 1. In Mode 0, TL0 acts as a logarith-

mic prescaler driving TH0 (see Figure 15-6). The PSC0 bits in TCONB control the prescaler

value. In Mode 1, TL0 provides linear prescaling with an 8-bit auto-reload from RL0 (see Figure

15-7).

Figure 15-5. Asymmetrical Pulse Width Modulation

Table 15-3.

TCONB

– Timer/Counter Control Register B

TCONB = 91H

Reset Value = 0010 0100B

Not Bit Addressable

PWM1EN

PWM0EN

PSC12

PSC11

PSC10

PSC02

PSC01

PSC00

Bit

Symbol

Function

PWM1EN

Configures Timer 1 for Pulse Width Modulation output on T1 (P3.5).

PWM0EN

Configures Timer 0 for Pulse Width Modulation output on T0 (P3.4).

PSC12

PSC11

PSC10

Prescaler for Timer 1 Mode 0. The number of active bits in TL1 equals PSC1 + 1. After reset PSC1 = 100B which

enables 5 bits of TL1 for compatibility with the 13-bit Mode 0 in AT89S2051.

PSC02

PSC01

PSC00

Prescaler for Timer 0 Mode 0. The number of active bits in TL0 equals PSC0 + 1. After reset PSC0 = 100B which

enables 5 bits of TL0 for compatibility with the 13-bit Mode 0 in AT89C52.

PWM Output (T0)

Counter Value (TH0)

Compare Value (RH0)

AT89LP2052 датащи(PDF) 26 Page - ATMEL Corporation

AT89LP2052 датащи(HTML) 26 Page - ATMEL Corporation

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

датащи скачать

ссылки URL