PURPOSE: To constitute the driver into low performance driver, without altering the instruction format, by replacing the spare selection display from the third unit into the unit address converted to the unit address of the second unit corresponding to the third unit.
CONSTITUTION: If the spare selection display signal from the third unit FF1 to FFn is not present in normal cases, the first cable driver circuit CDo is in normal use condition with the control of the selection control circuit CHG, and the second cable driver circuit CD1 is in waiting condition, and the instruction including the unit address of the second unit delivered from the central processing unit CC is held at the register circuit REG, then it is delivered to the first signal bus circuit BUo via the circuit CDo. On the other hand, in the second unit DV10 to DVnO for existing system connected to the circuit BUo, the unit address including the instruction on the circuit BUo is identified, and in case of the unit itself designation, the load unit corresponding to the unit itself is driven according to the instruction. Accordingly, since the second unit and the load unit can be located near spacingly, the driver of low performance not requiring high speed and greater power driving can be used as the second unit.
ISHIZAWA AKIRA
MIURA MASAMI
SATOU ISAO
MAENO SHINICHI
NIPPON TELEGRAPH & TELEPHONE
NIPPON ELECTRIC CO
HITACHI LTD
FUJITSU LTD