AT90CAN128-16AE ATMEL Corporation, AT90CAN128-16AE Datasheet - Page 161

• Manufacturer Part Number: AT90CAN128-16AE
• Description: 8-bit Avr Microcontroller With 128K Bytes of Isp Flash And CAN Controller.flash (Kbytes) 128 Vcc (V) 2.7-5.5 EEPROM (Kbytes) 4 SRAM (bytes) 4K CAN (mess. Obj.) 15
• Manufacturer: ATMEL Corporation

Timing Example
Resolution of the PWM Signal
4250C–CAN–03/04
Waveform Generator)
Waveform Generator)
COM0A1
COM0A0
COM1C1
COM1C0
(From T/C1
(From T/C0
PORTB7
D
D
D
OC1C
OC0A
Q
Q
Q
Figure 74. Output Compare Modulator, Schematic
Figure 75 illustrates the modulator in action. In this example the Timer/Counter1 is set to
operate in fast PWM mode (non-inverted) and Timer/Counter0 uses CTC waveform
mode with toggle Compare Output mode (COMnx1:0 = 1).
Figure 75. Output Compare Modulator, Timing Diagram
In this example, Timer/Counter0 provides the carrier, while the modulating signal is gen-
erated by the Output Compare unit C of the Timer/Counter1.
The resolution of the PWM signal (OC1C) is reduced by the modulation. The reduction
factor is equal to the number of system clock cycles of one period of the carrier (OC0A).
In this example the resolution is reduced by a factor of two. The reason for the reduction
is illustrated in Figure 75 at the second and third period of the PB7 output when
PORTB7 equals zero. The period 2 high time is one cycle longer than the period 3 high
time, but the result on the PB7 output is equal in both periods.
(FPWM Mode)
(PORTB7 = 0)
(PORTB7 = 1)
(CTC Mode)
(Period)
OC1C
OC0A
clk
PB7
PB7
I/O
DATABUS
1
Modulator
0
1
DDRB7
D
2
Q
1
0
AT90CAN128
OC0A / OC1C / PB7
3
Vcc
Pin
161