diff --git a/USB-config-%26-command-protocol.md b/USB-config-%26-command-protocol.md
index bfdcb1a..8907f27 100644
--- a/USB-config-%26-command-protocol.md
+++ b/USB-config-%26-command-protocol.md
@@ -54,6 +54,7 @@ A list of all the currently-implemented modes:
 * SPI (serprog) command prefix (`0x13`): Perform a SPI command, see below.
 * I2C command prefix (`0x14`): Perform an I2C command, see below.
 * Temperature sensor command prefix (`0x15`): Perform a temperature sensor command, see below.
+* UART↔USB hardware flow control enable/disable (`0x16`): has a single argument byte, `0x00` to disable hardware flow control, any other value to enable. Baud rate and other line control settings are done using the standard USB-CDC line control things.
 
 #### SPI commands