UPD17708 datasheet(48/356 Pages) NEC

48 / 356 page

µPD17704, 17705, 17707, 17708, 17709

5.3.4 Cautions on Using Address Register

Because the address register is configured in 16 bits, it can specify an address up to FFFFH.

However, the program memory exists at addresses 0000H to 1FFFH in the case of

µPD17704, 0000H to

2FFFH in the case of the

µPD17705 and 17707 and 0000H to 3FFFH in the case of the µPD17708 and 17709.

Therefore, the maximum value that can be set to the address register of the

µPD17704 is address 1FFFH.

In the case of the

µPD17705 and 17707, it is address 2FFFH. In the case of the µPD17708 and 17709, it is

address 3FFFH.

5.4 Window Register (WR)

5.4.1 Configuration of window register

Figure 5-4 shows the configuration of the window register.

As shown in the figure, the window register consists of 4 bits of system register address 78H (WR).

Figure 5-4. Configuration of Window Register

5.4.2 Function of window register

The window register is used to transfer data with the register file (RF) to be described later.

Data transfer between the window register and register file is manipulated by using dedicated instructions

“PEEK WR, rf” and “POKE, rf WR” (rf: address of register file).

The following paragraphs (1) and (2) describe the operation of the window register when these instructions

are executed.

For further information, also refer to 8. REGISTER FILE (RF).

(1) “PEEK WR, rf” instruction

When this instruction is executed, the contents of the register file addressed by “rf” are transferred to

the window register.

(2) “POKE rf, WR” instruction

When this instruction is executed, the contents of the window register are transferred to the register file

addressed by “rf”.

Address

Name

Symbol

Bit

Data

Clock stop

78H

Window register

(WR)

Undefined

Retained

Power-ON reset

WDT&SP reset

CE reset

UPD17708 Datasheet(PDF) 48 Page - NEC

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