ADUC834 Analog Devices, ADUC834 Datasheet - Page 37

• Manufacturer Part Number: ADUC834
• Description: Precision Analog Microcontroller: 1MIPS 8052 MCU + 62kB Flash + 16/24-Bit ADC + 12-Bit DAC
• Manufacturer: Analog Devices

Specifications of ADUC834

• Mcu Core: 8052
• Mcu Speed (mips): 1
• Sram (bytes): 2304Bytes
• Gpio Pins: 34
• Adc # Channels: 4
• Other: PWM

PWM MODES OF OPERATION
Mode 0: PWM Disabled
The PWM is disabled, allowing P1.0 and P1.1 be used as normal.
Mode 1: Single-Variable Resolution PWM
In Mode 1, both the pulse length and the cycle time (period) are
programmable in user code, allowing the resolution of the PWM
to be variable.
PWM1H/L sets the period of the output waveform. Reducing
PWM1H/L reduces the resolution of the PWM output but
increases the maximum output rate of the PWM (e.g., setting
PWM1H/L to 65536 gives a 16-bit PWM with a maximum
output rate of 192 Hz (12.583 MHz/65536). Setting PWM1H/L
to 4096 gives a 12-bit PWM with a maximum output rate of
3072 Hz (12.583 MHz/4096)).
PWM0H/L sets the duty cycle of the PWM output waveform,
as shown in Figure 27.
Mode 2: Twin 8-Bit PWM
In Mode 2, the duty cycle of the PWM outputs and the resolution
of the PWM outputs are both programmable. The maximum
resolution of the PWM output is eight bits.
PWM1L sets the period for both PWM outputs. Typically this
will be set to 255 (FFh) to give an 8-bit PWM, although it is
possible to reduce this as necessary. A value of 100 could be
loaded here to give a percentage PWM (i.e., the PWM is accu-
rate to 1%).
The outputs of the PWM at P1.0 and P1.1 are shown in the
diagram below. As can be seen, the output of PWM0 (P1.0) goes
low when the PWM counter equals PWM0L. The output of
PWM1 (P1.1) goes high when the PWM counter equals PWM1H
and goes low again when the PWM counter equals PWM0H.
Setting PWM1H to 0 ensures that both PWM outputs start
simultaneously.
REV. A
Figure 27. PWM in Mode 1
PWM COUNTER
PWM1H/L
PWM0H/L
P1.0
0
–37–
Mode 3: Twin 16-Bit PWM
In Mode 3, the PWM counter is fixed to count from 0 to 65536
giving a fixed 16-bit PWM. Operating from the 12.58 MHz core
clock results in a PWM output rate of 192 Hz. The duty cycle
of the PWM outputs at P1.0 and P1.1 are independently
programmable.
As shown below, while the PWM counter is less than PWM0H/L,
the output of PWM0 (P1.0) is high. Once the PWM counter
equals PWM0H/L, then PWM0 (P1.0) goes low and remains
low until the PWM counter rolls over.
Similarly, while the PWM counter is less than PWM1H/L, the
output of PWM1 (P1.1) is high. Once the PWM counter equals
PWM1H/L, then PWM1 (P1.1) goes low and remains low until
the PWM counter rolls over.
In this mode, both PWM outputs are synchronized (i.e., once the
PWM counter rolls over to 0, both PWM0 (P1.0) and PWM1
(P1.1) will go high).
Figure 28. PWM Mode 2
Figure 29. PWM Mode 3
PWM COUNTER
PWM COUNTER
ADuC834
65536
PWM1H/L
PWM0H/L
0
P1.0
P1.1
PWM1L
PWM0H
PWM0L
PWM1H
P1.0
P1.1
0