p89lpc9351 NXP Semiconductors, p89lpc9351 Datasheet - Page 33

• 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
7.20.6 Timer overflow toggle output
7.22.1 CCU clock
7.22.2 CCUCLK prescaling
7.22.3 Basic timer operation
7.21 RTC/system timer
7.22 CCU
Timers 0 and 1 can be configured to automatically toggle a port output whenever a timer
overflow occurs. The same device pins that are used for the T0 and T1 count inputs are
also used for the timer toggle outputs. The port outputs will be a logic 1 prior to the first
timer overflow when this mode is turned on.
The P89LPC9351 has a simple RTC that allows a user to continue running an accurate
timer while the rest of the device is powered down. The RTC can be a wake-up or an
interrupt source. The RTC is a 23-bit down counter comprised of a 7-bit prescaler and a
16-bit loadable down counter. When it reaches all logic 0s, the counter will be reloaded
again and the RTCF flag will be set. The clock source for this counter can be either the
CPU clock (CCLK) or the XTAL oscillator. Only power-on reset and watchdog reset will
reset the RTC and its associated SFRs to the default state.
The 16-bit loadable counter portion of the RTC is readable by reading the RTCDATL and
RTCDATH registers.
This unit features:
The CCU runs on the CCUCLK, which is either PCLK in basic timer mode, or the output of
a PLL. The PLL is designed to use a clock source between 0.5 MHz to 1 MHz that is
multiplied by 32 to produce a CCUCLK between 16 MHz and 32 MHz in PWM mode
(asymmetrical or symmetrical). The PLL contains a 4-bit divider to help divide PCLK into a
frequency between 0.5 MHz and 1 MHz.
This CCUCLK can further be divided down by a prescaler. The prescaler is implemented
as a 10-bit free-running counter with programmable reload at overflow.
The timer is a free-running up/down counter with a direction control bit. If the timer
counting direction is changed while the counter is running, the count sequence will be
reversed. The timer can be written or read at any time.
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A 16-bit timer with 16-bit reload on overflow.
Selectable clock, with prescaler to divide clock source by any integral number
between 1 and 1024.
Four compare/PWM outputs with selectable polarity
Symmetrical/asymmetrical PWM selection
Two capture inputs with event counter and digital noise rejection filter
Seven interrupts with common interrupt vector (one overflow, two capture, four
compare)
Safe 16-bit read/write via shadow registers.
Rev. 01 — 19 November 2008
8-bit microcontroller with 8-bit ADC
P89LPC9351
© NXP B.V. 2008. All rights reserved.
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