Questions Related to Short Messages

Is the module able to send short messages immediately after the power is turned on ?

No. This is because the authentication with the SIM card takes some time after the module is powered on. Therefore, it is better to wait for 30s before you send short messages, or ERROR 512 will occur. CALL READY function is added in versions after build 10 of SIM300 series. Users can enable or disable this function through AT+CIURC. When it is enabled, users can only send short messages and make calls after the module is powered on and receive CALL READY.
How does the module distinguish short messages from data when there's incoming data while the module is reading short messages ?

Short messages have a message header. Users are recommended to use AT+CIPHEAD=1 set data headers for data. In this way, +IPDXXX will be automatically added when there's incoming data.
What does "+CMS ERROR: 513" mean ?

There are unread messages on the SIM card.
What does "+CMS ERROR: 322" mean ?

The memory of the SIM card for short messages is full.

Refer to the message part in the APP NOTES.

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