Integrated circuit memory devices include an internal command generator and a memory control circuit responsive to an internal command generated by the internal command generator. The internal command generator is configured to generate an internal command in response to a combination of an independent command and at least one dependent command received in sequence by the memory device. For example, the internal command generator may be configured to require the independent command to follow the at least one dependent command in the sequence when generating the internal command from the combination of the independent and dependent commands. Alternatively, the internal command generator may be configured to require the independent command to precede the at least one dependent command in the sequence before generating the internal command from the combination of the independent and dependent commands. These independent and dependent commands may be received by the memory device as respective multi-bit external command signals.