Rev. 1.10
28
November 26, 2019
Rev. 1.10
29
November 26, 2019
HT68FB240
USB Low Speed Flash MCU
In Circuit Programming – ICP
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 4-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.
The Holtek Flash MCU to Writer Programming Pin correspondence table is as follows:
Holtek Writer Pins
MCU Programming Pins
Pin Description
ICPDA
UDN
Programming Serial Data/Address
ICPCK
RES
Programming Clock
VDD
VDD
Power Supply
VSS
VSS
Ground
The Program Memory can be programmed serially in-circuit using this 4-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 device are beyond the scope of this document and will
be supplied in supplementary literature.
During the programming process, taking control of the UDN
and
RES
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.
Note: * may be resistor or capacitor. The resistance of * must be greater than
300
Ω or the
capacitance of * must be less than 1nF.