Fujitsu 8FX User Manual

MB95630H Series
4 FUJITSU SEMICONDUCTOR LIMITED MN702-00009-2v0-E
CHAPTER 2 CPU
2.1 Dedicated Registers
2.1 Dedicated Registers
The CPU has dedicated registers: a program counter (PC), two registers for
arithmetic operations (A and T), three address pointers (IX, EP, and SP), and the
program status (PS) register. Each of the registers is 16 bits long. The PS
register consists of the register bank pointer (RP), direct bank pointer (DP), and
condition code register (CCR).
■ Configuration of Dedicated Registers
The dedicated registers in the CPU consist of seven 16-bit registers. As for the accumulator (A)
and the temporary accumulator (T), using only the lower eight bits of the respective registers is
also supported.
Figure 2.1-1 shows the configuration of the dedicated registers.
Figure 2.1-1 Configuration of Dedicated Registers
■ Functions of Dedicated Registers
●
Program counter (PC)
The program counter is a 16-bit counter which contains the memory address of the instruction
currently executed by the CPU. The program counter is updated whenever an instruction is
executed or an interrupt or a reset occurs. The initial value set immediately after a reset is the
mode data read address (0xFFFD).
● Accumulator (A)
The accumulator is a 16-bit register for arithmetic operation. It is used for a variety of
arithmetic and transfer operations of data in memory or data in other registers such as the
temporary accumulator (T). The data in the accumulator can be handled either as word (16-bit)
data or byte (8-bit) data. For byte-length arithmetic and transfer operations, only the lower
eight bits (AL) of the accumulator are used with the upper eight bits (AH) left unchanged. The
initial value set immediately after a reset is "0x0000".
Initial value
0xFFFD Program counter
Indicates the address of the current instruction.
0x0000 Accumu lator (A)
Temporary storage register for arithmetic operation and transfer
0x0000 Temporary accumulator (T)
Performs arithmetic operations with the accumulator.
0x0000 Index register
Indicates an index address.
0x0000 Extra pointer
Indicates a me
mory address.
0x0000 Stack pointer
Indicates the current stack location.
0x0030Program status
Stores a register bank pointer,
a direct bank pointer, and a condition code.
16 bits
PS
SP
EP
IX
PC
TH TL
AH AL
RP DP CCR
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Fujitsu 8FX Specifications

General

Brand	Fujitsu
Model	8FX
Category	Computer Hardware
Language	English