Rev. 2.10
32
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Rev. 2.10
33
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HT68F20/HT68F30/HT68F40/HT68F50/HT68F60
HT68FU30/HT68FU40/HT68FU50/HT68FU60
Enhanced I/O Flash Type 8-Bit MCU with EEPROM
HT68F20/HT68F30/HT68F40/HT68F50/HT68F60
HT68FU30/HT68FU40/HT68FU50/HT68FU60
Enhanced I/O Flash Type 8-Bit MCU with EEPROM
In Circuit Programming
The provision of Flash type Program Memory provides the user with a means of convenient and
easy upgrades and modifications to their programs on the same device.
As an additional convenience, Holtek has provided a means of programming the microcontroller
in-circuit using a 5-pin interface. This provides manufacturers with the possibility of manufacturing
their circuit boards complete with a programmed or un-programmed microcontroller, and then
programming or upgrading the program at a later stage. This enables product manufacturers to easily
keep their manufactured products supplied with the latest program releases without removal and
re-insertion of the device.
MCU Programming Pins
Function
PA0
Seria� Data Inp�t/O�tp�t
PA2
Seria� C�ock
RES
Device Reset
VDD
Power S�pp��
VSS
Gro�nd
The Program Memory and EEPROM data memory can both be programmed serially in-circuit using
this 5-wire interface. Data is downloaded and uploaded serially on a single pin with an additional
line for the clock. Two additional lines are required for the power supply and one line for the reset.
The technical details regarding the in-circuit programming of the devices are beyond the scope of
this document and will be supplied in supplementary literature.
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.
*
*
*
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
D A T A
C L K
V S S
R E S
V D D
W r i t e r C o n n e c t o r
S i g n a l s
M C U P r o g r a m m i n g
P i n s
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
MCU Pins
RES
PB0
DATA
PA0
CLK
PA2
Programmer and MCU Pins