HT82B40A HOLTEK [Holtek Semiconductor Inc], HT82B40A Datasheet - Page 10

• Manufacturer Part Number: HT82B40A
• Description: I/O MCU with USB Interface
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

tempreg1 db
tempreg2 db
mov a,06h
mov tblp,a
tabrdl
dec tblp
tabrdl
org F00h
dc
Because the TBLH register is a read-only register and
cannot be restored, care should be taken to ensure its
protection if both the main routine and Interrupt Service
Routine use the table read instructions. If using the table
read instructions, the Interrupt Service Routines may
change the value of TBLH and subsequently cause er-
rors if used again by the main routine. As a rule it is rec-
ommended that simultaneous use of the table read
instructions should be avoided. However, in situations
where simultaneous use cannot be avoided, the inter-
rupts should be disabled prior to the execution of any
main routine table-read instructions. Note that all table
related instructions require two instruction cycles to
complete their operation.
Data Memory
The Data Memory is a volatile area of 8-bit wide RAM
internal memory and is the location where temporary in-
formation is stored. Divided into two sections, the first of
these is an area of RAM where special function registers
are located. These registers have fixed locations and
are necessary for correct operation of the device. Many
of these registers can be read from and written to di-
rectly under program control, however, some remain
protected from user manipulation. The second area of
Data Memory is reserved for general purpose use. All
locations within this area are read and write accessible
under program control.
Structure
The two sections of Data Memory, the Special Purpose
and General Purpose Data Memory are located at con-
secutive locations. All are implemented in RAM and are
8 bits wide. The start address of the Data Memory for all
devices is the address 00H . Registers which are com-
Rev. 1.10
:
:
:
:
:
:
00Ah, 00Bh, 00Ch, 00Dh, 00Eh, 00Fh, 01Ah, 01Bh
:
:
tempreg1
tempreg2
?
?
; temporary register #1
; temporary register #2
; initialise table pointer - note that this address is referenced
; to the last page or present page
; transfers value in table referenced by table pointer to tempregl
; data at prog. memory address F06H transferred to tempreg1 and TBLH
; reduce value of table pointer by one
; transfers value in table referenced by table pointer to tempreg2
; data at prog.memory address F05H transferred to tempreg2 and TBLH
; in this example the data 1AH is transferred to
; tempreg1 and data 0FH to register tempreg2
; the value 00H will be transferred to the high byte register TBLH
; sets initial address of last page
10
mon to all microcontrollers, such as ACC, PCL, etc.,
have the same Data Memory address.
General Purpose Data Memory
All microcontroller programs require an area of
read/write memory where temporary data can be stored
and retrieved for use later. It is this area of RAM memory
that is known as General Purpose Data Memory. This
area of Data Memory is fully accessible by the user pro-
gram for both read and write operations. By using the
can be set or reset under program control giving the
user a large range of flexibility for bit manipulation in the
Data Memory.
Note:
SET [m].i and CLR [m].i instructions, individual bits
Most of the Data Memory bits can be directly
manipulated using the SET [m].i and CLR
[m].i with the exception of a few dedicated bits.
The Data Memory can also be accessed
through the memory pointer register MP.
Data Memory Structure
HT82B40R/HT82B40A
September 4, 2009