P89LPC915FDH datasheet(40/75 Pages) NXP

40 / 75 page

P89LPC915_916_917_5

Product data sheet

Rev. 05 — 15 December 2009

40 of 75

NXP Semiconductors

P89LPC915/916/917

8-bit microcontrollers with accelerated two-clock 80C51 core

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.

8.17.1 Mode 0

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.

8.17.2 Mode 1

Mode 1 is the same as Mode 0, except that all 16 bits of the timer register are used.

8.17.3 Mode 2

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.

8.17.4 Mode 3

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.

8.17.5 Mode 6

In this mode, the corresponding timer can be changed to a PWM with a full period of

256 timer clocks.

8.17.6 Timer overﬂow toggle output

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.

8.18 RTC/system timer

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.

P89LPC915FDH Datasheet(PDF) 40 Page - NXP Semiconductors

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