The number of General Purpose Input/Outputs is one major difference between these two parts. The CY7C6300x has twelve GPIOs and the CY7C6310x has sixteen GPIOs. Each of these products also come in different packages because of the difference in the number of IO's: The 12-GPIO CY7C6300x is available in 20-pin PDIP (-PC) and 20-pin SOIC (-SC) packages. The 16-GPIO CY7C6310x is available in 24-pin SOIC (-SC) and 24-pin QSOP (-QC) packages.
Note: The CY7C630xx/CY7C631xx are not recommended for new designs. Instead we recommend using the enCoRe II product line. It has advanced features such as the internal oscillator (no external 6MHz clock), internal 3.3V regulator (for pulling up D- as required by the USB spec), Combi USB/PS/2 interface supported, wake-up circuit (no external RC wake up circuit needed), SPI compatible, Low voltage reset, each GPIO is independently configurable in different modes,...
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enCoRe II USB