7702 datasheet(32/217 Pages) RENESAS

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CENTRAL PROCESSING UNIT (CPU)

2.1 Central processing unit

2–6

7702/7703 Group User’s Manual

2.1.7 Data bank register (DT)

The data bank register is an 8-bit register. In the following addressing modes using the data bank register,

the contents of this register is used as the high-order 8 bits (bank) of a 24-bit address to be accessed.

Use the LDT instruction to set a value to this register.

In the single-chip mode, make sure to fix this register to “0016”. It is because the access space of the

single-chip mode is the internal area within the bank 016.

This register is cleared to “0016” at reset.

qAddressing modes using data bank register

•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 is a 16-bit register. The contents of this register indicate the direct page area

which is allocated in bank 016 or in the space across banks 016 and 116. The following addressing modes

use the direct page register.

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

area. The space which extends to 256 bytes above that address is specified as a direct page.

The direct page register can contain a value from “000016” to “FFFF16.” When it contains a value equal to

or more than “FF0116,” the direct page area spans the space across banks 016 and 116.

When the contents of low-order 8 bits of the direct page register is “0016,” the number of cycles required

to generate an address is 1 cycle smaller than the number when its contents are not “0016.” Accordingly,

the access efficiency can be enhanced in this case.

This register is cleared to “000016” at reset.

Figure 2.1.4 shows a setting example of the direct page area.

qAddressing modes using direct page register

•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

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