+/** Enables the physical PDI interface on the target and enables access to the internal NVM controller.
+ *
+ * \return Boolean \c true if the PDI interface was enabled successfully, \c false otherwise
+ */
+bool XMEGANVM_EnablePDI(void)
+{
+ /* Enable PDI programming mode with the attached target */
+ XPROGTarget_EnableTargetPDI();
+
+ /* Store the RESET key into the RESET PDI register to keep the XMEGA in reset */
+ XPROGTarget_SendByte(PDI_CMD_STCS(PDI_REG_RESET));
+ XPROGTarget_SendByte(PDI_RESET_KEY);
+
+ /* Lower direction change guard time to 32 USART bits */
+ XPROGTarget_SendByte(PDI_CMD_STCS(PDI_REG_CTRL));
+ XPROGTarget_SendByte(0x02);
+
+ /* Enable access to the XPROG NVM bus by sending the documented NVM access key to the device */
+ XPROGTarget_SendByte(PDI_CMD_KEY);
+ for (uint8_t i = sizeof(PDI_NVMENABLE_KEY); i > 0; i--)
+ XPROGTarget_SendByte(PDI_NVMENABLE_KEY[i - 1]);
+
+ /* Wait until the NVM bus becomes active */
+ return XMEGANVM_WaitWhileNVMBusBusy();
+}
+
+/** Removes access to the target's NVM controller and physically disables the target's physical PDI interface. */
+void XMEGANVM_DisablePDI(void)
+{
+ XMEGANVM_WaitWhileNVMBusBusy();
+
+ /* Clear the RESET key in the RESET PDI register to allow the XMEGA to run - must perform this until the
+ * change takes effect, as in some cases it takes multiple writes (silicon bug?).
+ */
+ do
+ {
+ /* Clear reset register */
+ XPROGTarget_SendByte(PDI_CMD_STCS(PDI_REG_RESET));
+ XPROGTarget_SendByte(0x00);
+
+ /* Read back the reset register, check to see if it took effect */
+ XPROGTarget_SendByte(PDI_CMD_LDCS(PDI_REG_RESET));
+ } while (XPROGTarget_ReceiveByte() != 0x00);
+
+ XPROGTarget_DisableTargetPDI();
+}
+