NEC PD754244 Manuel D’Utilisation
CHAPTER 3 FEATURES OF ARCHITECTURE AND MEMORY MAP
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User’s Manual U10676EJ3V0UM
3.3 Memory-Mapped I/O
The
µPD754244 employs memory-mapped I/O that maps peripheral hardware units such as I/O ports and timers
to addresses F80H to FFFH on the data memory space, as shown in Figure 3-2. Therefore, no special instructions
to control the peripheral hardware units are provided, and all the hardware units are controlled by using memory
manipulation instructions. (Some mnemonics that make the program easy to read are provided for hardware control.)
To manipulate peripheral hardware units, the addressing modes shown in Table 3-4 can be used.
Table 3-4. Addressing Modes Applicable to Peripheral Hardware Unit Manipulation
Applicable Addressing Mode
Hardware Units
Bit manipulation
Specified in direct addressing mode mem.bit with
All hardware units that can be
MBE = 0 or (MBE = 1, MBS = 15)
manipulated in 1-bit units
Specified in direct addressing mode fmem.bit regardless
IST1, IST0, MBE, RBE
of setting of MBE and MBS
IE
×××, IRQ×××, PORTn.×
Specified in indirect addressing mode pmem.@L
BSBn.
×
regardless of setting of MBE and MBS
PORTn.
×
4-bit manipulation
Specifies in direct addressing mode mem with MBE = 0
All hardware units that can be
or (MBE = 1, MBS = 15)
manipulated in 4-bit units
Specified in register indirect addressing @HL with
(MBE = 1, MBS = 15)
(MBE = 1, MBS = 15)
8-bit manipulation
Specified in direct addressing mem with MBE = 0 or
All hardware units that can be
(MBE = 1, MBS = 15), where mem is even number.
manipulated in 8-bit units
Specified in register indirect addressing @HL with
MBE = 1, MBS = 15, where contents of L register
are even number
MBE = 1, MBS = 15, where contents of L register
are even number
Example
CLR1
MBE
; MBE = 0
SET1
TM0. 3
; Starts timer 0
EI
IE0
; Enables INT0
DI
IET1
; Disables INTT1
SKTCLR
IRQ2
; Tests and clears INT2 request flag
SET1
PORT3, @L ; Sets port 3
IN
A, PORT6
; A
← port 6