diff --git a/Variant-USART.md b/Variant-USART.md
index 2a745c2..8d8b0a5 100644
--- a/Variant-USART.md
+++ b/Variant-USART.md
@@ -20,7 +20,15 @@ Commands are send as binary frames with following structure:<br />
 - Checksum(unsigned int16) : XOR checksum
 
 The least significant byte comes first (little endian).<br>
-The FOC firmware will discard frames that are not starting with proper start frame and not ending with correct checksum.<br />
+
+## Error rejection
+
+The FOC firmware will discard frames if:
+- Command length is not correct
+- Start frame is not correct
+- Checksum is not correct
+- 1 character inactivity on RX line while receiving the frame ([Idle Line Interrupt](https://github.com/1847123212/STM32_USART_DMA_RX#about-usart))
+
 A timeout will be triggered if no correct frame is received during the time specified with parameter SERIAL_TIMEOUT in config.h (160ms by default).<br />
 
 ## Calibration: