HT46R01A
Memory Pointers - MP0, MP1
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Two Memory Pointers, known as MP0 and MP1 are pro-
vided. These Memory Pointers are physically imple-
mented in the Data Memory and can be manipulated in
the same way as normal registers providing a conve-
nient way with which to address and track data. When
any operation to the relevant Indirect Addressing Regis-
ters is carried out, the actual address that the
microcontroller is directed to, is the address specified by
the related Memory Pointer, bit 7 of the Memory
Pointers is not required to address the full memory
space. It must be noted that when bit 7 of the Memory
Pointers for these devices is read, a value of ²1² will be
returned. The following example shows how to clear a
section of four Data Memory locations already defined as
locations adres1 to adres4.
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Special Purpose Data Memory
data .section ¢data¢
adres1
adres2
adres3
adres4
block
db ?
db ?
db ?
db ?
db ?
code .section at 0 ¢code¢
org 00h
start:
mov a,04h
mov block,a
mov a,offset adres1; Accumulator loaded with first RAM address
; setup size of block
mov mp0,a
; setup memory pointer with first RAM address
loop:
clr IAR0
inc mp0
sdz block
jmp loop
; clear the data at address defined by MP0
; increment memory pointer
; check if last memory location has been cleared
continue:
The important point to note here is that in the example shown above, no reference is made to specific Data Memory ad-
dresses.
Rev. 1.10
11
August 13, 2008
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