In my
design of an application where I need to communicate with the outside world
thro' serial interface - I have to use a 16-Bit Microcontroller. I want to keep
cost of my design low - Shall I use an internal oscillator or go by external
resonator?
If you are referring to the internal oscillator in a microcontroller such as the ones from Silicon Labs, they come for free with with the part and there is no additional PCB space required. The question then becomes "is the accuracy good enough over temperature and voltage variations". Serial communications typically can tolerate a variation of up to 5%.
Bruce,
There are several options depending on what features you want. They are enhanced versions of the 8051. Some of the ones you should look at are:
C8051F930 - will run down to 1.8VDC, 64K FLASH, 4K RAM
C8051F340 - 2 serial channels, 64K FLASH, 4K RAM, USB
C8051F124 - 2 serial channels, 12 bit ADC, 128K FLASH, 4K RAM
All of these have SMBus and at least on SPI channels
From my own experience, external resonators are far more cost effective, provided you source the part from a tier 1 supplier, pick the right package and load capacitors (i.e. 0402 or smaller case size + trace length capacitance...)
Philips LPC900 oscillators are specified with +/- 2.5% over temp range and voltage range. They also offer very nice combinations of serial interfaces already in the low cost devices.
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