Rev. 1.10
20
November 26, 2019
Rev. 1.10
21
November 26, 2019
HT68FB240
USB Low Speed Flash MCU
ISP Bootloader
The devices provide the ISP Bootloader function to upgrade the software in the Flash memory.
The user can select to use the ISP Bootloader application software provided by Holtek IDE tool or
to create his own Bootloader software. When the Holtek Bootloader software is selected, that will
occupy 0.5K words area in the Flash memory. The accompanyimg diagram illustrates the Flash
memory structure with Holtek Bootloader software.
Bootloader
Last Page
0000H
0D00H
0DFFH
HT68FB240
Flash Program Memory Registers
There are two address registers, four 16-bit data registers and one control register. The control
register is located in Bank 1 and the other registers are located in Bank 0. Read and Write operations
to the Flash memory are carried out in 16-bit data operations using the address and data registers
and the control register. Several registers control the overall operation of the internal Flash Program
Memory. The address registers are named FARL and FARH, the data registers are named FDnL and
FDnH, and the single control register is named FCR. As the FARL and FDnL registers are located
in Bank 0, they can be directly accessed in the same was as any other Special Function Register.
The FARH, FDnH, FCR and FRCR registers however, being located in Bank 1, cannot be addressed
directly and can only be read from or written to indirectly using the MP1 Memory Pointer and
Indirect Addressing Register, IAR1.
Program Memory Register List
Register
Name
Bit
7
6
5
4
3
2
1
0
FARL
D7
D6
D5
D4
D3
D2
D1
D0
FARH
—
—
—
—
D11
D10
D9
D8
FD0L
D7
D6
D5
D4
D3
D2
D1
D0
FD0H
D15
D14
D13
D12
D11
D10
D9
D8
FD1L
D7
D6
D5
D4
D3
D2
D1
D0
FD1H
D15
D14
D13
D12
D11
D10
D9
D8
FD2L
D7
D6
D5
D4
D3
D2
D1
D0
FD2H
D15
D14
D13
D12
D11
D10
D9
D8
FD3L
D7
D6
D5
D4
D3
D2
D1
D0
FD3H
D15
D14
D13
D12
D11
D10
D9
D8
FCR
CFWEN
FMOD2
FMOD1
FMOD0
BWT
FWT
FRDEN
FRD
FRCR
—
—
—
FSWRST
—
—
—
CLWB