Rev. 1.71
30
April 11, 2017
Rev. 1.71
31
April 11, 2017
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
Bank Pointer – BP
For this series of devices, the Data Memory is divided into two banks, Bank0 and Bank1. Selecting
the required Data Memory area is achieved using the Bank Pointer. Bit 0 of the Bank Pointer is used
to select Data Memory Banks 0~1.
The Data Memory is initialised to Bank 0 after a reset, except for a WDT time-out reset in the Power
Down Mode, in which case, the Data Memory bank remains unaffected. It should be noted that the
Special Function Data Memory is not affected by the bank selection, which means that the Special
Function Registers can be accessed from within any bank. Directly addressing the Data Memory
will always result in Bank 0 being accessed irrespective of the value of the Bank Pointer. Accessing
data from Bank1 must be implemented using Indirect Addressing.
BP Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
—
—
—
DMBP0
R/W
—
—
—
—
—
—
—
R/W
POR
—
—
—
—
—
—
—
0
B
it 7 ~ 1
Unimplemented, read as "0"
B
it 0
DMBP0
: Select Data Memory Banks
0: Bank 0
1: Bank 1
Accumulator – ACC
The Accumulator is central to the operation of any microcontroller and is closely related with
operations carried out by the ALU. The Accumulator is the place where all intermediate results
from the ALU are stored. Without the Accumulator it would be necessary to write the result of
each calculation or logical operation such as addition, subtraction, shift, etc., to the Data Memory
resulting in higher programming and timing overheads. Data transfer operations usually involve
the temporary storage function of the Accumulator; for example, when transferring data between
one user-defined register and another, it is necessary to do this by passing the data through the
Accumulator as no direct transfer between two registers is permitted.
Program Counter Low Register – PCL
To provide additional program control functions, the low byte of the Program Counter is made
accessible to programmers by locating it within the Special Purpose area of the Data Memory. By
manipulating this register, direct jumps to other program locations are easily implemented. Loading
a value directly into this PCL register will cause a jump to the specified Program Memory location,
however, as the register is only 8-bit wide, only jumps within the current Program Memory page are
permitted. When such operations are used, note that a dummy cycle will be inserted.
Look-up Table Registers – TBLP, TBLH
These two special function registers are used to control operation of the look-up table which is
stored in the Program Memory. TBLP is the table pointer and indicate the location where the table
data is located. Its value must be setup before any table read commands are executed. Its value
can be changed, for example using the “INC” or “DEC” instructions, allowing for easy table data
pointing and reading. TBLH is the location where the high order byte of the table data is stored
after a table read data instruction has been executed. Note that the lower order table data byte is
transferred to a user defined location.
