AS (Address Strobe Input) – A positive going address strobe pulse serves to demultiplex the bus. The
falling edge of AS/ALE causes the address to be latched within the DS12C887. The next rising edge that
occurs on the AS bus will clear the address regardless of whether  CS is asserted. Access commands
should be sent in pairs.

看看原版英文资料吧,那些漏洞百出的中文翻译会让你抓狂的

下降沿锁存地址,下一个上升沿清除地址

哪里不对？上升沿锁存地址，然后读该地址的字节内容。读完以后清除地址信息（应该是置“高阻状态”），解除对地址总线的占用，以便其他程序使用地址总线。