NEC PD750008 Manuale Utente

The µPD750008 employs memory-mapped I/O, which maps peripheral hardware such as timers and I/O

ports to addresses F80H to FFFH in data memory space as shown in Figure 3-2.  This means that there is

no particular instruction to control peripheral hardware, but all peripheral hardware is controlled using memory

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

To manipulate peripheral hardware, the addressing modes listed in Table 3-4 can be used.

Applicable addressing mode

Applicable hardware

Bit

Direct addressing mode specifying mem.bit with

All hardware

manipulation

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

allowing bit manipulation

Direct addressing mode specifying fmem.bit regardless of

IST1, IST0, MBE, RBE,

MBE and MBS setting

IExxx, IRQxxx, PORTn.x

Indirect addressing mode specifying pmem.@L regardless of

BSBn.x

MBE and MBS setting

PORTn.x

4-bit

Direct addressing mode specifying mem with

All hardware allowing 4-bit

manipulation

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

manipulation

Register indirect addressing mode specifying @HL with
(MBE = 1, MBS = 15)

8-bit

Direct addressing mode specifying mem (even address) with

All hardware allowing 8-bit

manipulation

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

manipulation

Register indirect addressing mode specifying @HL
(with the L register containing an even number) with
MBE = 1 and MBS = 15

Figure 3-7 summarizes the I/O map of the µPD750008.

The items in the figure have the following meanings:

• Symbol : Name representing 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 at a time in hardware manipulation

O

: Bit manipulation is possible in units of the indicated number of bits (1, 4, or 8 bits).

Ð

: Particular bits can be manipulated.  For these bits, see Remarks.

–

: Bit manipulation is impossible in units of the indicated number of bits (1, 4, or 8 bits).

• Bit manipulation addressing:

Bit manipulation addressing applicable in hardware bit manipulation