Why do we use R0 and R1 in indirect addressing mode of 8051? This question has been answered in one of the threads but i want to know how come 8051 can only select one bit for R0 or R1 and R2 to R7 is not possible. sorry if i sound a little stupid. i am a newbee in 8051
To understand why instructions are designed in such formats, you need to study how the hex codes (for the respective opcodes) are designed/encoded in any processor/controller. Each instruction bit (or a group of bits) specify the operation, source, destination etc info. _look at the "encoding" specified for each instruction in files referred by Erik_
PS: Dont bother that much about _why is it designed in such a way?_ In engineering, each design has a lot of reasons, and a lot of smart people out there have worked to design it as it is.