P89LPC920FDH PHILIPS [NXP Semiconductors], P89LPC920FDH Datasheet - Page 23

• Manufacturer Part Number: P89LPC920FDH
• Description: 8-bit microcontrollers with two-clock 80C51 core 2 kB/4 kB/8 kB 3 V low-power Flash with 256-byte data RAM
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
9397 750 14469
Product data
8.15.1 Reset vector
8.16.1 Mode 0
8.16.2 Mode 1
8.16 Timers/counters 0 and 1
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:
Following reset, the P89LPC920/921/922/9221 will fetch instructions from either
address 0000h or the Boot address. The Boot address is formed by using the Boot
Vector as the high byte of the address and the low byte of the address = 00h.
The Boot address will be used if a UART break reset occurs, or the non-volatile Boot
Status bit (BOOTSTAT.0) = 1, or the device is forced into ISP mode during power-on
(see P89LPC920/921/922/9221 User’s Manual ). Otherwise, instructions will be
fetched from address 0000H.
The P89LPC920/921/922/9221 has two general purpose counter/timers which are
upward compatible with the standard 80C51 Timer 0 and Timer 1. Both can be
configured to operate either as timers or event counter. An option to automatically
toggle the T0 and/or T1 pins upon timer overflow has been added.
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 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.
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.
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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.
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. 08 — 15 December 2004
P89LPC920/921/922/9221
8-bit microcontrollers with two-clock 80C51 core
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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