| 摘要 |
<p>PURPOSE:To reduce used ICs in number and also to simplify the circuit constitution by providing a switch which turns ON-OFF only the power supply of a bus output stage IC. CONSTITUTION:Before a printed substrate is inserted into a bus in process of online process, switch 700 which turns ON-OFF only the power supply of a gate IC at the output stage is set to side (b). Afterwards, inserting the printed substrate makes power supply Vcc active at point A. Shortly after the insertion of the printed substrate, the whole circuit constitution is unstable and output signal 703 and bus control signal 504 of a FF inside of the interface are active for T1. When Vcc becomes stable, VccA702 becomes effective as an initialization signal, and signals 703 and 504 are both reset. With switch 700 set to side (a) next, the initialization signal is reset and the power supply of IC 704 at the bus output stage is put to work, so that the interface will be enabled to operate. At the time when the print substrate is pulled out next, switch 700 is set side (b) before the operation, so that even if Vcc becomes unstable, unneeded data will not be sent out to the bus.</p> |
