Fujitsu CM71-00101-5E User Manual

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CHAPTER 3  REGISTER DESCRIPTIONS

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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.

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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.

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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

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