p89lpc904 NXP Semiconductors, p89lpc904 Datasheet - Page 25

• Manufacturer Part Number: p89lpc904
• Description: 8-bit Microcontrollers With Two-clock Accelerated 80c51 Core 1 Kb 3 V Byte-erasable Flash With 8-bit A/d Converter
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 13521
Preliminary data
8.17.1 Mode 0
8.17.2 Mode 1
8.17.3 Mode 2
8.17.4 Mode 3
8.17 Timers/counters 0 and 1
8.18 Real-Time clock/system timer
Reset can be triggered from the following sources:
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:
The P89LPC904 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.
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.
The P89LPC904 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
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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.
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.
Rev. 02 — 25 June 2004
8-bit microcontrollers with two-clock accelerated 80C51 core
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
P89LPC904
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