Browsing through the webs brought me to http://www.hdsc.com.cn/page.aspx...id=23&f=cn which appears to describe a family of mcus based on the 80251 (yes, the 16-bitter).
http://www.hdsc.com.cn/upload/20160906140352xz.pdf appears to be a user manual. Tables starting at page 107 show that it's not cycle-compatible, an enhancement rather.

Some language skills may be needed... :-)

JW