SWRU629A September 2024 – February 2025
The CC35xxE requires xSPI external flash memory for execution code. The LP-EM-CC35X1 features an onboard external flash (U5).
The xSPI signals from the CC35xxE are part of the VDDSF IO ring, and this voltage can be defined as either 1.8V or 3.3V, depending on the external flash used. The default voltage of VDDSF on the LP-EM-CC35X1 is 1.8V. This voltage provides the reference voltage for the xSPI lines from the CC35xxE and supply voltage to the external flash.
If users want to use a flash that interfaces at 3.3V instead, then R42 can be assembled on the right two solder pads instead of the left (left pads = 1.8V, right pads = 3.3V). The R42 is on the left solder pads, therefore, the VDDSF voltage is 1.8V, as shown in Figure 2-19.