URC (Unsolicited Result Code)

AT command 관련 문서를 보던중, URC가 나오길래.. 찾아봄.
URC 이런거였구만요.

----------------------------------------------------------------------------------------------------------------from Embedded Freaks.
URC is the message that is sent from the ME(Mobile Equipment, eg. GSM/GPRS/CDMA modem) that's not the result of the AT command.

Here's some examples :

RING is sent when the modem is called.
CONNECTED is sent when the modem answer the call.

You can think of URC as modem's soft Interrupt.
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아하, 그리고, AT command 사이사이에는 약간의 delay가 필요하다는 내용도 있네요.

Give delay for Each AT command

All of AT Commands are ended with OK.
Once you've received the string, you need to wait (ie.100ms)
before launching another AT command. By this way,
you will not crash your AT command with the URC from modem.

The modem will gurantee that it will not issue URC
while AT command is processed. But it will issue URC once the AT command is finishied.
That's why you have to wait.

퍼온 싸이트.
http://embeddedfreak.wordpress.com/2008/08/19/handling-urc-unsolicited-result-code-in-hayes-at-command/