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3.2 Dedicated Register
specified after the reset operation is undefined.
r Temporary Accumulator (T)
The temporary accumulator is an auxiliary 16-bit arithmetic operation register.
It handles
arithmetic operations using data in the accumulator (A).
When arithmetic operations in the
accumulator (A) are handled in word units (16 bits), data in the temporary accumulator is
handled in word units. Otherwise, it is handled in byte units (8 bits). When arithmetic operations
are handled in byte units, only the lower 8 bits (TL) in the temporary accumulator are used; the
upper 8 bits (TH) are not used.
When an MOV instruction is used to transfer data into the accumulator (A), data stored in the
accumulator is automatically transferred to the temporary accumulator before it is transferred.
For data transfer in byte units, the upper 8 bits of the temporary accumulator (TH) does not
change. The initial value of the temporary accumulator specified after the reset operation is
undefined.
r Index register (IX)
The index register is a 16-bit register that stores an index address. The index register is used
together with a 1-byte offset (-128 to +127). It generates a memory address for accessing data
by adding a sign-extended offset to the index address. The initial value of the index register
specified after the reset operation is undefined.
r Extra-pointer (EP)
The extra-pointer is a 16-bit register.
Data in the extra-pointer is handled as the memory
address for accessing data.
The initial value of the extra-pointer specified after the reset
operation is undefined.
r Stack pointer (SP)
The stack pointer is a 16-bit register that stores an address that is used to call an interrupt or
subroutine, or to which a stack/recovery instruction makes a reference. While a program is
being executed, the value of the stack pointer indicates the address of the latest data put in the
stack. The initial value of the stack pointer specified after the reset operation is undefined.
r Program status (PS) register
The program status is a 16-bit control register. The upper 8 bits of the program status register
is the register bank pointer (RP) used to indicate the address of a general-purpose register
bank.
The lower 8 bits are the condition code register (CCR) that composes flags for indicating the
CPU status. Because these 8-bit registers comprise the program status register, they cannot be
accessed.
(Only instructions MOVW A, PS and MOVW PS, A access the program status
register.)
Note:
For details on how to use the dedicated register, see the F2MC-8L MB89600 Series
Programming Manual.