Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 637

Operation error
Error code Description
(SD0)
2820H There is no NULL code (00H) in the setting area specified by (s) and later in the device/label memory.
There is no NULL code (00H) in the setting area specified by (d) and later in the device/label memory.
2821H The device numbers for storing the strings in the devices specified by (s) and (d) are overlapping.
3405H The number of characters in the string specified by (s) exceeds 16383.
The number of characters in the string specified by (d) exceeds 16383.
3406H The number of characters in the concatenated string ((s)+(d)) exceeds 16383.
The entire string after concatenate processing cannot be stored in the setting area specified by (d) in the device/label memory. (The
number of required points is insufficient.)
7 APPLICATION INSTRUCTIONS
7.8 String Processing Instructions
7
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