--- a/rvinterf/asyncshell/helpfile	Fri Feb 08 00:49:34 2019 +0000
+++ b/rvinterf/asyncshell/helpfile	Fri Feb 08 02:14:53 2019 +0000
@@ -17,6 +17,7 @@
 tch		TCH commands, see help tch
 tch-dl		Enable/disable TCH downlink forwarding on the target
 tgtreset	Send reset/reboot ETM command packet to the target
+unterm		Send unterminated strings to ATI
 
 To get help on any command, type help and the command keyword.
 
@@ -172,3 +173,23 @@
 === tgtreset
 This command sends a reset/reboot request ETM command packet to the target.
 
+=== unterm
+unterm <arbitrary text>
+
+This command sends everything after the unterm command keyword to the AT command
+interpreter (ATI) in the target firmware via the FreeCalypso-defined "AT"
+RVTMUX channel.  Unlike the more classic str command, strings sent with unterm
+are marked as unterminated, meaning that the receiving code in ATI will not
+automatically add the usual terminating CR or ^Z at the end, and will instead
+wait for a continuation.  This mechanism allows long command or message strings
+to be sent in pieces, with the first and any intermediate pieces sent as unterm
+and the last piece sent with str, causing the entire string to be acted upon.
+This unterm extension to the AT-over-RVTMUX mechanism was added to our Magnetite
+and Selenite firmwares in early 2019, allowing this mechanism to be used for
+sending and writing SMS in PDU mode, which requires longer strings than the
+maximum that can be sent in one piece over RVTMUX.
+
+Any time you send anything to ATI, fc-shell automatically performs the
+equivalent of an enable ati command so you can see ATI's responses; any
+asynchronous output from ATI is also enabled as a side effect.
+