Program Counter (Pc) - Fujitsu FR Family Instruction Manual

CHAPTER 3 REGISTER DESCRIPTIONS
3.3.1

Program Counter (PC)

This register indicates the address containing the instruction that is currently
executing. Following a reset, the contents of the PC are set to the reset entry address
contained in the vector table.
■ Overview of the Program Counter
This register indicates the address containing the instruction that is currently executing. The value of the
lowest bit is always read as "0", and therefore all instructions must be written to addresses that are
multiples of 2.
■ Program Counter Functions
●
Lowest Bit Value of Program Counter
The value of the lowest bit in the program counter is read as "0" by the internal circuits in the FR family
device. Even if "1" is written to this bit, it will be treated as "0" for addressing purposes. A physical cell
does exist for this bit, however, the lowest bit value remains "0" even when the program address value is
incremented and therefore the value of this bit is always "0" except following a branching operation.
Because the internal circuits in the FR family device are designed to read the value of the lowest bit as "0",
all instructions must be written to addresses that are multiples of 2.
●
Program Counter Initial Value
Following a reset, the contents of the PC are set to the reset entry address contained in the vector table.
Because initialization is applied first to the table base register (TBR), the value of the reset vector address
will be "000FFFFC
18
".
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