Philips Semiconductors

User’s Manual - Preliminary -

 

 

 

 

 

 

CLOCKS

P89LPC901/902/903

 

Quartz crystal or ceramic resonator

The oscillator must be configured in one of the following modes:

-Low Frequency Crystal

-Medium Frequency Crystal

-High Frequency Crystal

*A series resistor may be required to limit crystal drive levels. This is especially

important for low frequency crystals.

 

P89LPC901

 

XTAL1

*

XTAL2

 

Figure 2-1: Using the Crystal Oscillator - P89LPC901

Oscillator Option Selection- P89LPC901

The oscillator option is selectable either by the FOSC2:0 bits in UCFG1 or by the RTCS1:0 bits in RTCCON. If the FOSC2:0 bits select an OSCCLK source of either the internal RC oscillator or the WDT oscillator, then the RTCS1:0 bits will select the oscillator option for the crystal oscillator. Otherwise, the crystal oscillator option is selected by FOSC2:0. See Table 6-1 and Table 6-2.

Clock Output - P89LPC901

The P89LPC901 supports a user selectable clock output function on the XTAL2 / CLKOUT pin when no crystal oscillator is being used. This condition occurs if another clock source has been selected (on-chip RC oscillator, watchdog oscillator, external clock input on X1) and if the Real-Time clock is not using the crystal oscillator as its clock source. This allows external devices to synchronize to the P89LPC901. This output is enabled by the ENCLK bit in the TRIM register

The frequency of this clock output is 1/2 that of the CCLK. If the clock output is not needed in Idle mode, it may be turned off prior to entering Idle, saving additional power. Note: on reset, the TRIM SFR is initialized with a factory preprogrammed value. Therefore when setting or clearing the ENCLK bit, the user should retain the contents of bits 5:0 of the TRIM register. This can be done by reading the contents of the TRIM register (into the ACC for example), modifying bit 6, and writing this result back into the TRIM register. Alternatively, the "ANL direct" or "ORL direct" instructions can be used to clear or set bit 6 of the TRIM register.

On-Chip RC oscillator Option

The P89LPC901/902/903 has a 6-bit field within the TRIM register that can be used to tune the frequency of the RC oscillator. During reset, the TRIM value is initialized to a factory pre-programmed value to adjust the oscillator frequency to 7.373 MHz, ±1%. (Note: the initial value is better than 1%; please refer to the datasheet for behavior over temperature). End user applications can write to the TRIM register to adjust the on-chip RC oscillator to other frequencies. Increasing the TRIM value will decrease the oscillator frequency.

2003 Dec 8

28

Page 27 Page 29
Page 28
Image 28
Philips P89LPC903, P89LPC902 Oscillator Option Selection- P89LPC901, Clock Output P89LPC901, On-Chip RC oscillator Option
Page 27 Page 29

P89LPC903, P89LPC902, P89LPC901 specifications

The Philips P89LPC901, P89LPC902, and P89LPC903 are a series of 8-bit microcontrollers designed for embedded system applications. These models, which belong to the LPC900 series, are notable for their affordability and versatility, making them an attractive choice for both hobbyists and professional developers.

One of the core features of the P89LPC901, P89LPC902, and P89LPC903 microcontrollers is their powerful 8-bit architecture. Operating at clock speeds up to 20 MHz, they deliver efficient performance suited for a range of tasks. Each model includes a comprehensive instruction set that supports various data manipulation and arithmetic functions, enabling extensive programming capabilities.

These microcontrollers come with built-in memory, with configurations that vary among the three models. The P89LPC901 typically features 4 KB of Flash memory and 256 bytes of RAM, while the P89LPC902 and P89LPC903 offer enhanced memory options. This Flash memory allows for reprogrammability, making it easier to update and modify applications as needed.

Another significant characteristic of the LPC900 series is their integrated peripherals. These models are equipped with a variety of I/O ports, allowing for easy interfacing with other devices and components. The P89LPC901 supports up to 32 I/O pins, while the P89LPC902 and P89LPC903 provide additional features such as analog-to-digital converters (ADCs), timers, and serial communication interfaces. This broad range of peripherals empowers developers to design complex applications without needing extra hardware.

Power consumption is also a key consideration for microcontroller applications. The P89LPC901, P89LPC902, and P89LPC903 are designed with low power consumption in mind, making them ideal for battery-operated devices and energy-efficient projects. They can operate in various power modes, allowing for greater flexibility in deployment.

In terms of technology, these microcontrollers utilize advanced CMOS technology, ensuring high reliability and durability. Their design offers a robust solution for numerous applications, including consumer electronics, industrial controls, and automation systems.

In summary, the Philips P89LPC901, P89LPC902, and P89LPC903 microcontrollers present an attractive combination of performance, integrated peripherals, low power consumption, and versatility. Their features cater to a wide array of applications, keeping them relevant in a rapidly evolving technology landscape. For hobbyists and professionals alike, these microcontrollers represent a reliable foundation for embedded system development.
Top Page Image Contents