89LPC925 查看數據表（PDF） - Philips Electronics

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89LPC925

8-bit microcontrollers with accelerated two-clock 80C51 core 4 kB/8 kB 3 V low-power Flash with 8-bit A/D converter

Philips Electronics 

Philips Semiconductors

P89LPC924/925

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

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 and Timer 1 have five operating modes (modes 0, 1, 2, 3 and 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

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.

8.18 Real-Time clock/system timer

The P89LPC924/925 has a simple Real-Time clock that allows a user to continue

running an accurate timer while the rest of the device is powered-down. The

Real-Time clock can be a wake-up or an interrupt source. The Real-Time clock 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. The clock source for this counter can be either the CPU clock (CCLK)

or the XTAL oscillator, provided that the XTAL oscillator is not being used as the CPU

clock. If the XTAL oscillator is used as the CPU clock, then the RTC will use CCLK as

its clock source. Only power-on reset will reset the Real-Time clock and its

associated SFRs to the default state.

9397 750 13459

Product data

Rev. 02 — 15 June 2004

© Koninklijke Philips Electronics N.V. 2004. All rights reserved.

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