Rainbow-electronics ATtiny28L Bedienungsanleitung PDF herunterladen (Seite 29)

ATtiny28L/V

1062E–10/01

Hardware Modulator ATtiny28 features a built-in hardware modulator connected to a high-current output pad,

PA2. The hardware modulator generates a configurable pulse train. The on-time of a

pulse can be set to a number of chip clock cycles. This is done by configuring the Modu-

lation Control Register (MODCR).

Modulation Control Register –

MODCR

• Bits 7..3 – ONTIM4..0: Modulation On-time

This 5-bit value +1 determines the number of clock cycles the output pin PA2 is active

(low).

• Bits 2..0 – MCONF2..0: Modulation Configuration Bits 2, 1 and 0

These three bits determine the relationship between the on- and off-times of the modu-

lator, and thereby the duty-cycle. The various settings are shown in Table 13. The

minimum and maximum modulation period is also shown in the table. The minimum

modulation period is obtained by setting ONTIM to zero, while the maximum period is

obtained by setting ONTIM to 31. The configuration values for some common oscillator

and carrier frequencies are listed in Table 15. The relationship between oscillator fre-

quency and carrier frequency is:

If the MCONF register is set to 111, the carrier frequency will be equal to the oscillator

frequency.

Note: In the high-frequency mode, the output is gated with the clock signal. Thus, the on- and off-times will be dependent on the clock

input to the MCU. Also note that when changing from this mode directly to another modulation mode, the output will have a

small glitch. Thus, PA2 should be set to stop the modulated output before changing from this mode.

Bit 76543 2 1 0

$02

ONTIM4 ONTIM3 ONTIM2 ONTIM1 ONTIM0 MCONF2 MCONF1 MCONF0 MODCR

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

Initial Value 0 0 0 0 0 0 0 0

fcarrier

fosc

On-time Off-time+

()

-----------------------------------------------------=

Table 13. MCONF2..0 Effect on Duty-cycle and Modulation Period

MCONF2..0 On-time Off-time Duty-cycle Min Period Max Period Comment

000 X X 100% X X Unmodulated output

001 ONTIM+1 ONTIM+1 50% 2 CK 64 CK

010 ONTIM+1 2 x (ONTIM+1) 33% 3 CK 96 CK

011 ONTIM+1 3 x (ONTIM+1) 25% 4 CK 128 CK

100 2 x (ONTIM+1) ONTIM+1 67% 3 CK 96 CK

101 3 x (ONTIM+1) ONTIM+1 75% 4 CK 128 CK

110 Reserved

111 X X Note 1 1 CK 1 CK High-frequency output

1 2 ... 24 25 26 27 28 29 30 31 32 33 34 ... 74 75

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