AN2027 - PSoC® 1 - 32.768 kHz External Crystal Oscillator
Last Updated: 12/11/2012
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Version: *E
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| Many microcontroller applications require a timing source more accurate than the typical internal oscillator. An external crystal can provide a solution. These crystals are used with an external crystal oscillator (ECO) to generate clocks as accurate as +/-50 parts per million. PSoC® 1 can implement an ECO that uses a 32.768-kHz crystal. |
PSoC 1 microcontroller’s external crystal oscillator (ECO) can be used as a reference for timekeeping and other low-speed (<32 kHz) operations. It can also act as the reference for the phase-locked loop (PLL) mode of the internal main oscillator (IMO). The PLL uses the 32.768 kHz input to generate a more accurate 24-MHz clock signal. This is used for operations that require an accurate high-speed clock such as dual-tone multifrequency (DTMF) signal generation and serial communications. Optimal performance from the ECO for each of these functions requires different external components and control register settings.
Example Project |
Supported H/W and S/W |
Supported PSoC1 Devices |
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PSoC Designer Version |
H/W Kit |
CY8C20xxx |
CY8C21xxx |
CY8C22xxx |
CY8C23xxx |
CY8C24xxx |
CY8C27xxx |
CY8C28xxx |
CY8C29xxx |
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No |
N/A |
CY3210-PSoCEVAL1 |
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x23A, x94 |
x43 |
x |
x66 |
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Related Application Notes:
Domain Tags: Xtal, Clocking
Related Knowledge Base: PSoC Designer, Xtal, ECO
Spec No: 001-40399;
Sunset Owner: PMAD;
Secondary Owner: GULA;
Sunset Date: 09/17/11
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