
Rev. 1.21
24
�ove��e� ��� 2�1�
Rev. 1.21
25
�ove��e� ��� 2�1�
HT66F488/HT66F489
A/D Flash MCU with EEPROM
HT66F488/HT66F489
A/D Flash MCU with EEPROM
RAM Data Memory
The Data Memory is an 8-bit wide RAM internal memory and is the location where temporary
information is stored.
Divided into two types, the first of Data Memory 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 directly 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 Data Memory is divided into several sectors, all of which are implemented in 8-bit wide
Memory. Each of the Data Memory sectors is categorized into two types, the Special Purpose Data
Memory and the General Purpose Data Memory.
The start address of the Special Purpose Data Memory for all devices is the address 00H while the
start address of the General Purpose Data Memory is the address 80H. The Special Purpose Data
Memory registers are accessible in all sectors, with the exception of the EEC register at address
40H, which is only accessible in Sector 1.
Device
Capacity
Sectors
HT66F488
HT66F48�
Gene�al Pu�pose: 384×8
�: 8�H~FFH
1: 8�H~FFH
2: 8�H~FFH
Special
Purpose
Data Memory
General
Purpose
Data Memory
00H
7FH
80H
FFH
Sector 0
40H in sector 1
Sector 0
Sector 1
Sector 2
Data Memory Structure
General Purpose Data Memory
There are 384 bytes of general purpose memory which are arranged in 80H~FFH of Sector 0~Sector
2. 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. The general purpose data memory is fully accessible by the user program for both
read and writing operations. By using the "SET [m].i" and "CLR [m].i" instructions individual
bits can be set or reset under program control giving the user a large range of flexibility for bit
manipulation in the Data Memory.