The MC68HC11 has two 8-bit accumulators (A and B), one 16-bit accumulator
(D) formed by A and B; where A is the MSB and B is the LSB. The microcontroller
also has two 16-bit index registers, namely X and Y. A 16-bit stackpointer
(SP) and a 16 bit programcounter (PC). The condition-code-register, or
flag-register, has 8 flags: