P89LPC915FDH datasheet(42/72 Pages) PHILIPS

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Philips Semiconductors

P89LPC915/916/917

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

Product data

Rev. 04 — 17 December 2004

42 of 72

9397 750 14397

Reset can be triggered from the following sources:

• External reset pin (during power-up or if user conﬁgured via UCFG1. This option

must be used for an oscillator frequency above 12 MHz.)

• Power-on detect

• Brownout detect

• Watchdog Timer

• Software reset

• UART break character detect reset.

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 logic 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.

9.16 Timers/counters 0 and 1

The P89LPC915/916/917 devices have two general purpose counter/timers which

are upward compatible with the standard 80C51 Timer 0 and Timer 1. An option to

automatically toggle the T0 pin upon timer overﬂow has been added. In addition an

option to toggle the T1 pin upon overﬂow has been added on the P89LPC917. In the

‘Timer’ function, the register is incremented every machine cycle. In the ‘Counter’

function, the register of Timer 0 is incremented in response to a 1-to-0 transition at its

external input pin. This external input is sampled once very 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, and 2 are the same for both

Timers/Counters. Mode 3 is different.

9.16.1

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.

9.16.2

Mode 1

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

9.16.3

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.

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