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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 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 sixteen 8-bit
registers.
Figure 2-5 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 2-6 shows the
stack.
· 16-bit registers
E registers (extended registers)
(E0 to E7)
R registers
(R0 to R7)
Figure 2-5 Usage of General Registers
· 8-bit registers
RH registers
(R0H to R7H)
RL registers
(R0L to R7L)
Rev. 5.00, 12/03, page 33 of 1088
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