HT82A520R HOLTEK [Holtek Semiconductor Inc], HT82A520R Datasheet - Page 12

• Manufacturer Part Number: HT82A520R
• Description: Full Speed USB 8-Bit OTP MCU with SPI
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

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 but the length of each memory section is dic-
tated by the type of microcontroller chosen. The start
address of the Data Memory for all devices is the ad-
dress 00H . Registers which are common to all
Note:
Rev.1.00
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
12
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.
SET [m].i and CLR [m].i instructions individual bits
HT82A520R/HT82A620R
October 23, 2009