Memory-Mapped I/O; Addressing Modes Applicable To Peripheral Hardware Unit Manipulation - NEC PD754144 User Manual

CHAPTER 3 FEATURES OF ARCHITECTURE AND MEMORY MAP

3.3 Memory-Mapped I/O

The µ PD754244 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
Bit manipulation Specified in direct addressing mode mem.bit with
MBE = 0 or (MBE = 1, MBS = 15)
Specified in direct addressing mode fmem.bit regardless
of setting of MBE and MBS
Specified in indirect addressing mode pmem.@L
regardless of setting of MBE and MBS
4-bit manipulation Specifies in direct addressing mode mem with MBE = 0
or (MBE = 1, MBS = 15)
Specified in register indirect addressing @HL with
(MBE = 1, MBS = 15)
8-bit manipulation Specified in direct addressing mem with MBE = 0 or
(MBE = 1, MBS = 15), where mem is even number.
Specified in register indirect addressing @HL with
MBE = 1, MBS = 15, where contents of L register
are even number
Example CLR1
SET1
EI
DI
SKTCLR
SET1
IN
50
Applicable Addressing Mode
MBE ; MBE = 0
TM0. 3 ; Starts timer 0
IE0 ; Enables INT0
IET1 ; Disables INTT1
IRQ2 ; Tests and clears INT2 request flag
PORT3, @L ; Sets port 3
; A ← port 6
A, PORT6
User's Manual U10676EJ3V0UM
Hardware Units
All hardware units that can be
manipulated in 1-bit units
IST1, IST0, MBE, RBE
IE×××, IRQ×××, PORTn.×
BSBn.×
PORTn.×
All hardware units that can be
manipulated in 4-bit units
All hardware units that can be
manipulated in 8-bit units