HT56R24 View Datasheet(PDF) - Holtek Semiconductor
Part Name
Description
MFG CO.
'HT56R24' PDF : 134 Pages View PDF
HT56R22/HT56R23/HT56R24/HT56R25/HT56R26
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 pro-
grammers by locating it within the Special Purpose area
of the Data Memory. By manipulating this register, direct
jumps to other program locations are easily imple-
mented. Loading a value directly into this PCL register
will cause a jump to the specified Program Memory lo-
cation, however, as the register is only 8-bit wide, only
jumps within the current Program Memory page are per-
mitted. When such operations are used, note that a
dummy cycle will be inserted.
Bank Pointer - BP
Depending upon which device is used, the Program and
Data Memory is divided into several banks. Selecting
the required Program and Data Memory area is
achieved using the Bank Pointer.
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 ac-
cessed irrespective of the value of the Bank Pointer. Ac-
cessing data from banks other than Bank 0 must be
implemented using Indirect addressing.
As both the Program Memory and Data Memory share
the same Bank Pointer Register, care must be taken
during programming.
Device
7
HT56R22
HT56R23
¾
HT56R24
¾
HT56R25
¾
HT56R26
¾
· BP Register
¨ HT56R22/HT56R23
Bit
7
Name
¾
R/W
¾
POR
¾
6
¾
¾
¾
PMBP1
6
¾
¾
¾
Bit
5
4
3
¾
¾
¾
¾
¾
¾
PMBP0
¾
DMBP3
PMBP0 DMBP4 DMBP3
BP Registers List
5
4
3
¾
¾
¾
¾
¾
¾
¾
¾
¾
Bit 7 ~ 2
Bit 1 ~ 0
Unimplemented, read as ²0²
DMBP1 ~ DMBP0: Select Data Memory Banks
00: Bank 0
01: Reserved
10: Bank 2
11: Undefined
2
¾
DMBP2
DMBP2
DMBP2
2
¾
¾
¾
1
DMBP1
DMBP1
DMBP1
DMBP1
1
DMBP1
R/W
0
0
DMBP0
DMBP0
DMBP0
DMBP0
0
DMBP0
R/W
0
Rev. 1.30
25
December 26, 2014
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