EM73962A
4-BIT MICROCONTROLLER
There are three addressing modes in the data memory :
(1) Indirect addressing mode:
The bank is selected by P9.3. When P9.3 is cleared to "0", the bank 0 is selected.
When P9.3 is set to "1", the bank 1 is selected. The address in the bank are specified by the HL registers.
P9.3
HR LR
RAM address
PROGRAM EXAMPLE: Load the data of RAM address "143h" to RAM address "023h".
SEP P9,3 ; P9.3← 1
LDL #3h ; LR← 3
LDH #4h ; HR← 4
LDAM
; Acc← RAM[134h]
CLP P9,3 ; P9.3← 0
LDL #2h ; LR← 2
LDH #3h ; HR← 3
STAM
; RAM[023h]← Acc
(2) Direct addressing mode:
The bank is selected by P9.3. When P9.3 is cleared to "0", the bank 0 is selected.
When P9.3 is set to "1", the bank 1 is selected. The address in the bank are directly specified by 8 bits of the
second byte in the instruction field.
instruction field
xxxxxxxx
P9.3
xxxxxxxx
RAM address
PROGRAM EXAMPLE: Load the data of RAM address "143h" to RAM address "023h".
SEP P9,3 ; P9.3← 1
LDA 43h ; Acc← RAM[134h]
CLP P9,3 ; P9.3← 0
STA 23h ; RAM[023h]← Acc
(3) Zero-page addressing mode:
The zero-page is the bank 0 (address 000h~00Fh). The address are the lower 4 bits of the second byte in the
instruction field.
instruction field
yyyy
yyyy
0000
0
RAM address
PROGRAM EXAMPLE: Write immediate "0Fh" to RAM address "005h".
STD #0Fh, 05h ; RAM[05h]← 0Fh
* This specification are subject to be changed without notice.
10.8.2001
7
ELAN [ ELAN MICROELECTRONICS CORP ]
