Data Memory - Holtek HT66F20-1 Manual

HT66F20-1/HT66F30-1/HT68F20-1/HT68F30-1
Flash MCU with EEPROM
During the programming process the RES pin will be held low by the programmer disabling the
normal operation of the microcontroller and taking control of the PA0 and PA2 I/O pins for data
and clock programming purposes. The user must there take care to ensure that no other outputs are
connected to these two pins.

Data Memory

The Data Memory is a volatile area of 8-bit wide RAM internal memory and is the location where
temporary information is stored.
Structure
Divided into two sections, the first of these is an area of RAM, known as the Special Function Data
Memory. Here are located registers which 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 known as the General Purpose Data Memory, which is reserved
for general purpose use. All locations within this area are read and write accessible under program
control. The Special Purpose Data Memory registers are accessible in all banks, with the exception
of the EEC register at address 40H, which is only accessible in Bank 1. Switching between the
different Data Memory banks is achieved by setting the Bank Pointer to the correct value. The start
address of the Data Memory for all devices is the address 00H.
Rev. 1.40
W r i t e r C o n n e c t o r
S i g n a l s
W r i t e r _ V D D
R E S
D A T A
C L K
W r i t e r _ V S S
*
T o o t h e r C i r c u i t
Note: * may be resistor or capacitor. The resistance of * must be
greater than 1kΩ or the capacitance of * must be less than 1nF.
Programmer Pin
RES
DATA
CLK
Programmer and MCU Pins
�9
M C U P r o g r a m m i n g
P i n s
V D D
R E S
D A T A
C L K
V S S
* *
MCU Pins
PB0
PA0
PA�
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