Special Function Register Description; Indirect Addressing Registers - Iar0, Iar1, Iar2; Memory Pointers - Mp0, Mp1H/Mp1L, Mp2H/Mp2L - Holtek HT67F2350 Manual

Special Function Register Description

Most of the Special Function
However, several registers require a separate description in this section.
Indirect Addressing Registers – IAR0, IAR1, IAR2
The Indirect Addressing Registers, IAR0, IAR1 and IAR2, although having their locations in normal
RAM register space, do not actually physically exist as normal registers. The method of indirect
addressing for RAM data manipulation uses these Indirect Addressing Registers and Memory
Pointers, in contrast to direct memory addressing, where the actual memory address is specified.
Actions on the IAR0, IAR1 and IAR2 registers will result in no actual read or
these registers but rather to the memory location specified by their corresponding Memory Pointers,
MP0, MP1L/MP1H or MP2L/MP2H. Acting as a pair, IAR0 and MP0 can together access data
only from Sector 0 while the IAR1 register together with MP1L/MP1H register pair and IAR2
register together with MP2L/MP2H register pair can access data from any Data Memory sector. As
the Indirect Addressing Registers are not physically implemented, reading the Indirect Addressing
Registers indirectly will return a result of "00H" and writing to the registers indirectly will result in
no operation.
Memory Pointers – MP0, MP1H/MP1L, MP2H/MP2L
Five Memory Pointers, known as MP0, MP1L, MP1H, MP2L and MP2H, are provided. These
Memory Pointers are physically implemented in the Data Memory and can be manipulated in the
same way as normal registers providing a convenient way with which to address and track data.
When any operation to the relevant Indirect Addressing Registers is carried out, the actual address
that the microcontroller is directed to is the address specified by the related Memory Pointer. MP0,
together with Indirect Addressing Register, IAR0, are used to access data from Sector 0, while
MP1L/MP1H together with IAR1 and MP2L/MP2H together with IAR2 are used to access data
from all data sectors according to the corresponding MP1H or MP2H register. Direct Addressing can
be used in all data sectors using the corresponding instruction which can address all available data
memory space.
Indirect Addressing Program Example
• Example 1
data .section 'data'
adres1 db ?
adres2 db ?
adres3 db ?
adres4 db ?
block db ?
code .section at 0 code
org 00h
start:
mov a,04h
mov block,a
mov a,offset adres1
mov mp0,a
loop:
clr IAR0
inc mp0
sdz block
jmp loop
continue:
Rev. 1.60
Advanced A/D Flash MCU with LCD & EEPROM
Register details will be described
; setup size of block
; Accumulator loaded with first RAM address
; setup memory pointer with first RAM address
; clear the data at address defined by MP0
; increment memory pointer
; check if last memory location has been cleared
72
HT67F2350/HT67F2360
HT67F2370/HT67F2390
in the relevant functional section.
write operation to
May 16, 2019