{"resolved":true,"match_type":"uuid","source_type":"original_book","book_id":"38270854-596f-4a26-8183-db8c968c6020","title":"编码 隐匿在计算机软硬件背后的语言","author":null,"edition":null,"publisher":null,"year":null,"isbn":"9787121181184","requested_by":"printed_page","book":{"source_type":"original_book","book_id":"38270854-596f-4a26-8183-db8c968c6020","id":"38270854-596f-4a26-8183-db8c968c6020","uuid":"38270854-596f-4a26-8183-db8c968c6020","title":"编码 隐匿在计算机软硬件背后的语言","normalized_title":"编码隐匿在计算机软硬件背后的语言","author":null,"edition":null,"publisher":null,"year":null,"isbn":"9787121181184","isbns":["9787121181184","0123456789","6044921875","3039331000","0000000000","0000000000000"],"parsed":true,"ai_readable":true,"document_type":"book","page_count":438,"navigation_url":"https://workshop.closeclaw.top/ai/book/38270854-596f-4a26-8183-db8c968c6020","title_url":"https://workshop.closeclaw.top/ai/title/%E7%BC%96%E7%A0%81%20%E9%9A%90%E5%8C%BF%E5%9C%A8%E8%AE%A1%E7%AE%97%E6%9C%BA%E8%BD%AF%E7%A1%AC%E4%BB%B6%E8%83%8C%E5%90%8E%E7%9A%84%E8%AF%AD%E8%A8%80","fixed_page_url_template":"https://workshop.closeclaw.top/ai/book/38270854-596f-4a26-8183-db8c968c6020/page/{printed_page}","path_api_url_template":"https://workshop.closeclaw.top/api/ai/book/38270854-596f-4a26-8183-db8c968c6020/page/{printed_page}","read_url":"https://workshop.closeclaw.top/api/ai/read/38270854-596f-4a26-8183-db8c968c6020","page_url":"https://workshop.closeclaw.top/api/ai/books/38270854-596f-4a26-8183-db8c968c6020/page","search_url":"https://workshop.closeclaw.top/api/ai/books/38270854-596f-4a26-8183-db8c968c6020/search"},"page":{"printed_page":341,"pdf_page":357,"physical_index":357,"physical_index_base":0,"printed_page_status":"recognized","page_sha256":"3c2f8aed266e92c5250093fe00f31417ac13e9d3df4b5f66c15f20ec233aee77"},"chapter":"编码隐匿在计算机软硬件背后的语言","content":"对应的16个编码间快速且重复地循环着，循环的速度必须足够快，以保证在按下并松开一个按键之前循环已经结束。\n\n4位计数器的输出同样也是2-4译码器和4-1数据选择器的输入。在没有按键按下的情况下，选择器的输入全都不为1，因此，其输出也不为1；一旦有某个按键被按下，而且与4位计数器某一特定输出相对应，那么选择器的输出就为1。例如，如果右上角对角线方向的第二个开关被按下，且计数器的输出是0110，选择器就会输出1，如下图所示。\n\n扫描码的位数是由键盘上按键的数目确定的。如果键盘上有64个键，就需要6位的扫描码，也就需要一个6位的计数器。用一个3-8译码器和一个8-1选择器就可以把这些按键组成一个8×8的阵列。如果键盘上的按键数目为65\\~128个，就需要7位的扫描码。你就可以用一个4-16译码器和一个8-1的选择器（或者一个3-8译码器和一个16-1选择\n\n21 总线\n\n341","previous_page":340,"next_page":342}