What will be the decimal value in register r23 after the execution of each of the following independent sequences of instructions. : What will be the decimal value in register r23 (if interpreted as a two’s complement number) after the execution of each of the following independent sequences of instructions?

sec(opcode) 1001 0100 0000 1000
clr(opcode) 0010 01Dd dddd DDDD (DDDDD=ddddd)
ror(opcode) 1001 010d dddd 0111

sec 
clr r23
ror r23

Answer: -128

Can someone tell me how to get the -128 (with clear explanation) from the instructions above?