参数资料
型号: ID80C52CXXX-16:D
厂商: ATMEL CORP
元件分类: 微控制器/微处理器
英文描述: 8-BIT, MROM, 16 MHz, MICROCONTROLLER, CDIP40
封装: CERAMIC, DIP-40
文件页数: 36/134页
文件大小: 3805K
130
8011Q–AVR–02/2013
ATmega164P/324P/644P
Using the ICRn Register for defining TOP works well when using fixed TOP values. By using
ICRn, the OCRnA Register is free to be used for generating a PWM output on OCnA. However,
if the base PWM frequency is actively changed by changing the TOP value, using the OCRnA as
TOP is clearly a better choice due to its double buffer feature.
In phase and frequency correct PWM mode, the compare units allow generation of PWM wave-
forms on the OCnx pins. Setting the COMnx1:0 bits to two will produce a non-inverted PWM and
an inverted PWM output can be generated by setting the COMnx1:0 to three (See Table on
page 133). The actual OCnx value will only be visible on the port pin if the data direction for the
port pin is set as output (DDR_OCnx). The PWM waveform is generated by setting (or clearing)
the OCnx Register at the compare match between OCRnx and TCNTn when the counter incre-
ments, and clearing (or setting) the OCnx Register at compare match between OCRnx and
TCNTn when the counter decrements. The PWM frequency for the output when using phase
and frequency correct PWM can be calculated by the following equation:
The N variable represents the prescaler divider (1, 8, 64, 256, or 1024).
The extreme values for the OCRnx Register represents special cases when generating a PWM
waveform output in the phase correct PWM mode. If the OCRnx is set equal to BOTTOM the
output will be continuously low and if set equal to TOP the output will be set to high for non-
inverted PWM mode. For inverted PWM the output will have the opposite logic values. If OCR1A
is used to define the TOP value (WGM13:0 = 9) and COM1A1:0 = 1, the OC1A output will toggle
with a 50% duty cycle.
13.10 Timer/Counter Timing Diagrams
The Timer/Counter is a synchronous design and the timer clock (clk
Tn) is therefore shown as a
clock enable signal in the following figures. The figures include information on when Interrupt
Flags are set, and when the OCRnx Register is updated with the OCRnx buffer value (only for
modes utilizing double buffering). Figure 13-10 shows a timing diagram for the setting of OCFnx.
Figure 13-10. Timer/Counter Timing Diagram, Setting of OCFnx, no Prescaling
Figure 13-11 shows the same timing data, but with the prescaler enabled.
f
OCnxPFCPWM
fclk_I/O
2 NTOP
----------------------------
=
clk
Tn
(clk
I/O/1)
OCFnx
clk
I/O
OCRnx
TCNTn
OCRnx Value
OCRnx - 1
OCRnx
OCRnx + 1
OCRnx + 2
相关PDF资料
PDF描述
ID80C52EXXX-25:D 8-BIT, MROM, 25 MHz, MICROCONTROLLER, CDIP40
ID80C52EXXX-L16:D 8-BIT, MROM, 16 MHz, MICROCONTROLLER, CDIP40
ID80C52XXX-25:D 8-BIT, MROM, 25 MHz, MICROCONTROLLER, CDIP40
ID80C52XXX-36SHXXX:D 8-BIT, MROM, 36 MHz, MICROCONTROLLER, CDIP40
ID80C52XXX-L16:D 8-BIT, MROM, 16 MHz, MICROCONTROLLER, CDIP40
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