You can use predefined symbols of the form ‘ r n h ’ and ‘ r n l ’ to refer to the H8/300 registers as sixteen 8-bit general-purpose registers. n is a digit from ‘ 0 ’ to ‘ 7 ’); for instance, both ‘ r0h ’ and ‘ r7l ’ are valid register names.
You can also use the eight predefined symbols ‘ r n ’ to refer to the H8/300 registers as 16-bit registers (you must use this form for addressing).
On the H8/300H, you can also use the eight predefined symbols ‘ er n ’ (‘ er0 ’ ... ‘ er7 ’) to refer to the 32-bit general purpose registers.
The two control registers are called
(program counter; a 16-bit register, except on the H8/300H where it is 24 bits) and
(condition code register; an 8-bit register).
is used as the stack pointer, and can also be called