P89LPC915_916_917 NXP Semiconductors, P89LPC915_916_917 Datasheet - Page 40

• Manufacturer Part Number: P89LPC915_916_917
• Description: The P89LPC915/916/917 are single-chip microcontrollers, available in low-cost packages,based on a high performance processor architecture that executes instructions in two tofour clocks, six times the rate of standard 80C51 devices
• Manufacturer: NXP Semiconductors

NXP Semiconductors
P89LPC915_916_917_5
Product data sheet
8.17.1 Mode 0
8.17.2 Mode 1
8.17.3 Mode 2
8.17.4 Mode 3
8.17.5 Mode 6
8.17.6 Timer overflow toggle output
8.18 RTC/system timer
In the ‘Timer’ function, the register is incremented every machine cycle.
In the ‘Counter’ function, the register is incremented in response to a 1-to-0 transition at its
corresponding external input pin, T0 or T1. In this function, the external input is sampled
once during every machine cycle.
Timer 0 has five operating modes (Modes 0, 1, 2, 3 and 6).
Timer 1 has four operating modes (Modes 0, 1, 2, and 3), except on the P89LPC917
where Timer 1 also has Mode 6. Modes 0, 1, 2 and 6 are the same for both
Timers/Counters. Mode 3 is different.
Putting either Timer into Mode 0 makes it look like an 8048 Timer, which is an 8-bit
Counter with a divide-by-32 prescaler. In this mode, the Timer register is configured as a
13-bit register. Mode 0 operation is the same for Timer 0 and Timer 1.
Mode 1 is the same as Mode 0, except that all 16 bits of the timer register are used.
Mode 2 configures the Timer register as an 8-bit Counter with automatic reload. Mode 2
operation is the same for Timer 0 and Timer 1.
When Timer 1 is in Mode 3 it is stopped. Timer 0 in Mode 3 forms two separate 8-bit
counters and is provided for applications that require an extra 8-bit timer. When Timer 1 is
in Mode 3 it can still be used by the serial port as a baud rate generator.
In this mode, the corresponding timer can be changed to a PWM with a full period of
256 timer clocks.
Timer 0 (and Timer 1 on the P89LPC917) 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 P89LPC915/916/917 have 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 ‘0’s, the counter will be reloaded
again and the RTCF flag will be set.
Rev. 05 — 15 December 2009
8-bit microcontrollers with accelerated two-clock 80C51 core
P89LPC915/916/917
© NXP B.V. 2009. All rights reserved.
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