In ACF／TCAM, a part of a basic transmission unit that is exchanged between the host access method and the network control program. It specifies a request for action by some device in the network. A BDU consists of a command and its modifiers, functional flags,and a data count.; 在通信系統(tǒng)軟件ACF／TCAM中,在主機(jī)存取方法和網(wǎng)絡(luò)控制程序之間進(jìn)行交換的基本傳輸 單元的一部分。它規(guī)定由網(wǎng)絡(luò)中的某一設(shè)備進(jìn)行工作的請(qǐng)求?；驹O(shè)備單元由一命令和它 的修飾語、功能標(biāo)志和數(shù)據(jù)計(jì)數(shù)組成。