EM73P982 datasheet(12/41 Pages) EMC

12 / 41 page

* This specification are subject to be changed without notice.

EM73P982

4-BIT MICROCONTROLLER

12.25.2001

P9.3

instruction field

RAM address

xxxx xxxx

instruction field

RAM address

yyyy

0000 yyyy

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.

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.

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.

PROGRAM EXAMPLE: Write immediate "0Fh" to RAM address "005h".

STD #0Fh, 05h ; RAM[05h]

← 0Fh

P9.3

RAM address

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