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CENTRAL PROCESSING UNIT (CPU)

7733 Group User’s Manual

2–6

2.1.7 Data bank register (DT)

The data bank register consists of 8 bits. In an addressing mode where the data bank register is used, the

contents of this register is processed as the high-order 8 bits (bank) of an address to be accessed, which

consists of 24 bits.

When setting a certain value to this register, execute the LDT instruction.

At reset, this register is cleared to “0016.”

g Addressing modes where the data bank register is used are listed below:

Direct • indirect

Direct • indexed X • indirect

Direct • indirect • indexed Y

Absolute

Absolute • bit

Absolute • indexed X

Absolute • indexed Y

Absolute • bit • relative

Stack pointer • relative • indirect • indexed Y

2.1.8 Direct page register (DPR)

The direct page register consists of 16 bits. The contents of this register specifies a direct page area to

bank 016 or an area which extends banks 016 and 116. The direct page area can be accessed with two

bytes (Note) by using the direct page addressing mode.

The contents of the direct page register indicates the base address (the lowest address) of a direct page

area which is extended to 256 bytes above this address.

Values from 000016 to FFFF16 can be set to the direct page register. When a certain value equal to or more

than “FF0116” is set to the direct page register, the direct page area is specified to an area which extends

banks 016 and 116. When the contents of low-order 8 bits of the direct page register is cleared to “0016,”

the number of cycles required to generate the address to be accessed is decremented by 1. Therefore,

efficient access is possible.

At reset, this register is cleared to “000016.”

Figure 2.1.4 shows a setting example of direct page areas.

Note: For the DIV and MPY instructions, the direct page area is accessed with 3 bytes.

When accumulator B is used, for each instruction, the number of instruction bytes is incremented

by 1.

g Addressing modes where the direct page register is used are listed below:

Direct

Direct • bit

Direct • indexed X

Direct • indexed Y

Direct • indirect

Direct • indexed X • indirect

Direct • indirect • indexed Y

Direct • indirect long

Direct • indirect long • indexed Y

Direct • bit • relative

2.1 Central processing unit

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