| 摘要 |
PURPOSE:To control the connection of an internal data bus to an external data bus having bus width different from that of the internal data bus by changing the bit data of the internal data bus connected to an effective input/output (I/O) terminal in accordance with an external control signal. CONSTITUTION:A bus connection control circuit has modes 2, 3 in addition to ordinary operation (modes 0, 1). Even when the bus width of the external data bus is 8 bits, the high-order 8 bits DB8-DB15 and low-order 8 bits DB0-DB7 of the internal data bus having 16-bit bus width can be transmitted/ received through I/O terminals P0-P7 by connecting the external data bus to the I/O terminals P0-P7 and alternately setting up the mode 2 and the mode 3 by a mode switching signal A, a data bus width selecting signal B and high-order/low-order digit switching signal C. Consequently, the connection of the internal data consisting of 16 bits to the external data bus consisting of 8 bits can be simply controlled. |
