P89LPC901FD datasheet(34/55 Pages) PHILIPS

34 / 55 page

Philips Semiconductors

P89LPC901/902/903

8-bit microcontrollers with two-clock 80C51 core

Product data

Rev. 04 — 21 November 2003

34 of 55

9397 750 12293

Reset can be triggered from the following sources:

• External reset pin (during power-up or if user conﬁgured via UCFG1)

• Power-on detect

• Brownout detect

• Watchdog Timer

• Software reset

• UART break character detect reset (P80LPC903).

For every reset source, there is a ﬂag in the Reset Register, RSTSRC. The user can

read this register to determine the most recent reset source. These ﬂag bits can be

cleared in software by writing a ‘0’ to the corresponding bit. More than one ﬂag bit

may be set:

• During a power-on reset, both POF and BOF are set but the other ﬂag bits are

cleared.

• For any other reset, previously set ﬂag bits that have not been cleared will remain

set.

8.16 Timers/counters 0 and 1

The P89LPC901/902/903 has two general purpose timers which are similar to the

standard 80C51 Timer 0 and Timer 1. These timers have four operating modes

(modes 0, 1, 2, and 3). Modes 0, 1, and 2 are the same for both Timers. Mode 3 is

different.

8.16.1

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.

8.16.2

Mode 1

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

8.16.3

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.

8.16.4

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.

8.16.5

Mode 6 (P89LPC901)

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

256 timer clocks.

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