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Standard 8051 8-Bit Flash MCU
HT85F2260/HT85F2270/HT85F2280
Flash Program Memory
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 four-line serial 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
Function
ICPDA
P0.0/ICPDA
P�og�amming Se�ial Data/Add�ess
ICPCK
RESET/ICPCK
P�og�amming Se�ial Clock
VDD
VDD
Powe� S�ppl�
VSS
VSS
G�o�nd
The Program Memory can be programmed serially in-circuit using the interface on pins ICPDA
and ICPCK. 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. 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. The Flash Program Memory Read/Write function is implemented using a
series of registers.
On-Chip Debug Support – OCDS
An EV chip, HT85V2280, is provided which includes all the HT85F2280 functions as well as an
“On-Chip Debug” interface for emulation of the HT85F2280/2270/2260 devices. To minimise
the difference between the real IC (the volume-production version) and the EV chip (the device
with the debug interface), a protocol converter is implemented to translate the external 2-wire
connections (TCK and TDA) into 4 internal JTAG signals (TCK, TMS, TDI, and TDO) and vice
versa. Users can use the EV chip device to emulate the real chip device behavior by connecting
the TDA and TCK pins to the related Holtek development tools. The TDA pin is the OCDS
Data/Address input/output pin while the TCK pin is the OCDS clock input pin. When users use the
EV chip for debugging, other functions which are shared with the TDA and TCK pins in the actual
MCU device will have no effect in the EV chip. However, the two OCDS pins which are pin-shared
with the ICP programming pins are still used as the Flash Memory programming pins for ICP. For
a more detailed OCDS description, refer to the corresponding user’s guide.