When Interfacing data length are 8-bit, transfer is performed is at a time through 8 ports, from DB0 to DB7.

When Interfacing data length are 4-bit, only ports from DB4 to DB7 are used at the data bus.

At first, the higher 4-bit (in case of 8-bit bus mode, the contents of DB4 to DB7), and then the lower 4-bit (in case of 8-bit bus mode, the contents of DB0 to DB3) are transferred. Therefore, the transfer performed twice. Busy Flag will outputs "HIGH" after the second transfer is ended.