45111 Datasheet, PDF (179/184 Pages) List of Unclassifed Manufacturers – 14-DAY MONEY BACK GUARANTEE

15 Appendix E: SX Data Sheet
15.6.1.3 Internal RC Mode
The SX offers an internal 4 MHz RC oscillator for timing insensitive operations. Using the internal
oscillator reduces external component count and system cost. The internal oscillator is configured via
the OSC4MHZ through OSC32KHZ device settings and the IRC Calibration settings. The SX-Key
Development software’s Configure dialog allows you to select the internal RC oscillator calibration
factor (Slow, 4 MHz or Fast). When using SASM, a directive (IRC_CAL) is also available, allowing
source code to have the proper fuse configuration embedded within it.
The IRC_4MHZ settings is used to adjust the operation of the internal RC oscillator to make it operate
within the target frequency range of 4 MHz ± 8%. The devices leave the factory untrimmed.
When using SASM, the SX-Key software automatically performs a calibration when the source code
contains the IRC_CAL IRC_4MHZ directive, and sets the calibration bits accordingly when it downloads
a program to the SX device.
Please note that the calibration process takes extra programming time. Therefore, when you don’t
intend to use the internal RC oscillator, place an IRC_CAL IRC_SLOW or IRC_CAL IRC_FAST directive
in your source code to always set the calibration bits to the lowest or highest value. In this case, the auto
calibrate step will be skipped.
SX-Key/Blitz Development System Manual 2.0 • Parallax, Inc. • Page 179