http://www.keil.com/support/man/docs/is51/is51_opcodes.htm lists 8051 instructions by HEX code. I had saw a line and make me confused. Why MOV direct, R8 appear in Hex Code 90 ? I mean, in other hex code, only can operate R0~R7. ex: INC/DEC/ADD/ORL/...etc
R8 only can apply in operation MOV direct, R8 ?
And question 2 is: because R9~R15 are not list in this table, would R9~R15 not be operated in C166 system?
Next question: What does Opcode 0x90 actually do...?
Since I couldn't find an actual opcode list in either of the three books of "the bible", I had to google for it.
Opcode 0x90 is ...
MOV DPTR,#data16
"I couldn't find an actual opcode list in either of the three books of 'the bible'"
Neither could I - which is why I didn't answer the question! ;-)