P89LPC920FDH PHILIPS [NXP Semiconductors], P89LPC920FDH Datasheet - Page 24

• 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
8.16.3 Mode 2
8.16.4 Mode 3
8.16.5 Mode 6
8.16.6 Timer overflow toggle output
8.18.1 Mode 0
8.17 Real-Time clock/system timer
8.18 UART
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.
In this mode, the corresponding timer can be changed to a PWM with a full period of
256 timer clocks.
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.
The P89LPC920/921/922/9221 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.
The P89LPC920/921/922/9221 has an enhanced UART that is compatible with the
conventional 80C51 UART except that Timer 2 overflow cannot be used as a baud
rate source. The P89LPC920/921/922/9221 does include an independent Baud Rate
Generator. The baud rate can be selected from the oscillator (divided by a constant),
Timer 1 overflow, or the independent Baud Rate Generator. In addition to the baud
rate generation, enhancements over the standard 80C51 UART include Framing
Error detection, automatic address recognition, selectable double buffering and
several interrupt options.The UART can be operated in 4 modes: shift register, 8-bit
UART, 9-bit UART, and CPU clock/32 or CPU clock/16.
Serial data enters and exits through RxD. TxD outputs the shift clock. 8 bits are
transmitted or received, LSB first. The baud rate is fixed at
frequency.
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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