UPD75238GJ 查看數據表（PDF） - NEC => Renesas Technology

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UPD75238GJ

4 BIT SINGLE-CHIP MICROCOMPUTER

NEC => Renesas Technology 

µPD75238

2.3 MEMORY-MAPPED I/O

The µPD75238 employs memory-mapped I/O, which maps peripheral hardware such as timers and I/O ports

to addresses F80H to FFFH in the data memory space as shown in Fig. 2-1. This means that there is no particular

instruction to control peripheral hardware, but all peripheral hardware is controlled using memory manipu-

lation instructions. (Some mnemonics for hardware control are available to make programs readable.)

To manipulate peripheral hardware, the addressing modes listed in Table 2-3 can be used.

The display data memory, key scan registers, and port H mapped to addresses 1A0H to 1FFH are to be

manipulated by specifying memory bank 1.

Table 2-3 Addressing Modes Applicable to Peripheral Hardware Mapped to Addresses F80H to FFFH

Applicable addressing mode

Applicable hardware

Bit manipulation Direct addressing mode specifying mem.bit with MBE = 0 or

(MBE = 1, MBS = 15)

All hardware allowing bit

manipulation

Direct addressing mode specifying fmem.bit regardless of MBE IST0, IST1, MBE, RBE,

and MBS setting

IE×××, IRQ×××, PORTn.0-3

Indirect addressing mode specifying pmem.@L regardless of

MBE and MBS setting

PORTn.

4-bit manipulation Direct addressing mode specifying mem with MBE = 0 or (MBE All hardware allowing 4-bit

= 1, MBS = 15)

manipulation

Register indirect addressing mode specifying @HL with (MBE

= 1, MBS = 15)

8-bit manipulation Direct addressing mode specifying mem (even address) with

MBE = 0 or (MBE = 1, MBS = 15)

All hardware allowing 8-bit

manipulation addressing

Register indirect addressing mode specifying @HL (with the L

register containing an even number) with (MBE = 1, MBS = 15)

Table 2-4 summarizes the I/O map of the µPD75238.

The items in Table 2-4 have the following meanings:

• Symbol: Name representing the address of incorporated hardware, which can be coded in the operand

field of an instruction

• R/W : Indicates whether the hardware allows read/write operation.

R/W: Both read and write operations possible

R : Read only

W : Write only

• Number of manipulatable bits:

Indicates the number of bits that can be processed in hardware manipulation

• Bit manipulation addressing:

Bit manipulation addressing applicable in hardware bit manipulation

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