p89lpc9351 NXP Semiconductors, p89lpc9351 Datasheet - Page 35

• Manufacturer Part Number: p89lpc9351
• Description: 8-bit Microcontroller With Accelerated Two-clock 80c51 Core 8 Kb 3 V Byte-erasable ?ash With 8-bit Adc
• Manufacturer: NXP Semiconductors

NXP Semiconductors
P89LPC9351_1
Preliminary data sheet
7.22.7 Alternating output mode
7.22.8 PLL operation
In asymmetrical mode, the user can set up PWM channels A/B and C/D as alternating
pairs for bridge drive control. In this mode the output of these PWM channels are
alternately gated on every counter cycle.
The PWM module features a Phase Locked Loop that can be used to generate a
CCUCLK frequency between 16 MHz and 32 MHz. At this frequency the PWM module
provides ultrasonic PWM frequency with 10-bit resolution provided that the crystal
frequency is 1 MHz or higher. The PLL is fed an input signal from 0.5 MHz to 1 MHz and
generates an output signal of 32 times the input frequency. This signal is used to clock the
timer. The user will have to set a divider that scales PCLK by a factor from 1 to 16. This
divider is found in the SFR register TCR21. The PLL frequency can be expressed as
shown in
Where: N is the value of PLLDV3:0.
PLL frequency
Fig 8.
Fig 9.
Symmetrical PWM
Alternate output mode
Equation
compare value
=
non-inverted
timer value
----------------- -
PCLK
N
inverted
1:
TOR2
+
Rev. 01 — 19 November 2008
1
0
8-bit microcontroller with 8-bit ADC
002aaa895
TOR2
COMPARE VALUE A (or C)
COMPARE VALUE B (or D)
0
PWM OUTPUT (OCA or OCC)
PWM OUTPUT (OCB or OCD)
TIMER VALUE
P89LPC9351
002aaa894
© NXP B.V. 2008. All rights reserved.
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