Merge branch 'patch-3' into 'master'

更新 README.md See merge request engintime/Dream-Logic/Intel-classic-chips/8253!4

Merge branch 'patch-3' into 'master'
5dfa238a · 李川 · 7cc503f0 · 54276692 · 5dfa238a
--- a/README.md
+++ b/README.md
 # 说明
 Intel 8253 可编程定时计数器
+# Datasheet
+[8253.pdf](8253.pdf)
 # 原理图
 ![raw svg](8253.dlsche.svg)
\ No newline at end of file