High Speed Data Communication Control Device Having an Uncompetitive Bus Construction

1. A data communication control device for transferring data between a system bus of a host computer and a network bus of a local area network, the control device comprising: a system bus interface means, directly connected with said system bus, for exchanging data with said system bus; a direct memory access means coupled with said system bus interface means; a network bus interface means, directly connected with said network bus, for exchanging data with said network bus; a two-port memory having first and second ports and directly connected with said network bus interface means and with said direct memory access means respectively, for temporarily holding data to be exchanged between said direct memory access means and said network bus interface means; a control logic independently connected to the two-port memory for independently controlling the two-port memory; a microprocessor directly connected to the first port of said two-port memory, said direct memory access means, said system bus interface means and said network bus interface means, for controlling data transfer between said network bus and said system bus; a first bus having four branches, each branch directly connecting said direct memory access means, said network bus interface means, the first port of said two-port memory and said microprocessor, respectively; a second bus directly connecting said direct memory access means to the second port of said two-port memory; a third bus directly and independently connecting said system bus interface means to said microprocessor; a fourth bus directly connecting said system bus interface means to said direct memory access means; a fifth bus directly connecting said system bus to said system bus interface means; and a sixth bus directly connecting said network bus to said network bus interface means, wherein transmission data from said system bus or reception data from said network bus is transmitted through the first, second, fourth, fifth and sixth buses.

2. The data communication control device as claimed in claim 1, wherein, in a data transmission mode from the system bus to the network bus, a command of data transmission from the system bus is transmitted to the system bus interface means, from which the transmission command is transmitted to the microprocessor through the third bus, transmission data from the system bus is transmitted through the system bus interface means to the second port of the two-port memory through the fourth bus, the direct memory access means, and the second bus, the two-port memory arranges the transmission data in accordance with control of the microprocessor to transmit the transmission data from the first port to the network bus interface means through the first bus, and the transmission data is transmitted from the network bus interface means to the network bus.

3. The data communication control device as claimed in claim 1, wherein, in a data reception mode from the network bus to the system bus, a command of data reception from the system bus is transmitted from the system bus interface means to the microprocessor through the third bus, the reception data from the network bus is transmitted through the network bus interface means to the first port of the two-port memory through the first bus, and the two-port memory receives the reception data when the microprocessor has received the reception command, and arranges the reception data to be transmitted from the second port of the two-port memory to the system bus through the second bus, the direct memory access means, the fourth bus, and the system bus interface means.