General Registers - Renesas Hitachi H8S/2194 Series Hardware Manual

2.4.2

General Registers

The CPU has eight 32-bit general registers. These general registers are all functionally alike and
can be used as both address registers and data registers. When a general register is used as a
data register, it can be accessed as a 32-bit, 16-bit, or 8-bit register. When the general registers
are used as 32-bit registers or address registers, they are designated by the letters ER (ER0 to
ER7).
The ER registers divide into 16-bit general registers designated by the letters E (E0 to E7) and R
(R0 to R7). These registers are functionally equivalent, providing a maximum of sixteen 16-bit
registers. The E registers (E0 to E7) are also referred to as extended registers.
The R registers divide into 8-bit general registers designated by the letters RH (R0H to R7H) and
RL (R0L to R7L). These registers are functionally equivalent, providing a maximum of sixteen
8-bit registers.
Figure 2.8 illustrates the usage of the general registers. The usage of each register can be
selected independently.
Address registers
32-bit registers
ER registers
(ER0 to ER7)
General register ER7 has the function of stack pointer (SP) in addition to its general-register
function, and is used implicitly in exception handling and subroutine calls. Figure 2.9 shows the
stack.
16-bit registers
E registers (extended registers)
(E0 to E7)
R registers
(R0 to R7)
Figure 2.8 Usage of General Registers
8-bit registers
RH registers
(R0H to R7H)
RL registers
(R0L to R7L)
Rev. 2.0, 11/00, page 25 of 1037