HT48CA0-1 Holtek Semiconductor, HT48CA0-1 Datasheet - Page 6

• Manufacturer Part Number: HT48CA0-1
• Description: (HT48RA0-1 / HT48CA0-1) Remote Type 8-Bit MCU
• Manufacturer: Holtek Semiconductor

www.DataSheet4U.com
counter lower-order byte register (PCL;06H), the table
pointer (TBLP;07H), the table higher-order byte register
(TBLH;08H), the status register (STATUS;0AH) and the
I/O registers (PA;12H, PB;14H, PC;16H). The remaining
space before the 20H is reserved for future expanded
usage and reading these locations will return the result
00H. The general purpose data memory, addressed
from 20H to 3FH, is used for data and control informa-
tion under instruction command.
All data memory areas can handle arithmetic, logic, in-
crement, decrement and rotate operations directly. Ex-
cept for some dedicated bits, each bit in the data
memory can be set and reset by the SET [m].i and CLR
[m].i instructions, respectively. They are also indirectly
accessible through memory pointer register (MP;01H).
Indirect Addressing Register
Location 00H is an indirect addressing register that is
not physically implemented. Any read/write operation of
[00H] accesses data memory pointed to by MP (01H).
Reading location 00H itself indirectly will return the re-
sult 00H. Writing indirectly results in no operation.
Rev. 1.40
RAM Mapping
6
The memory pointer register MP (01H) is a 7-bit register.
The bit 7 of MP is undefined and reading will return the
result 1 . Any writing operation to MP will only transfer
the lower 7-bit data to MP.
Accumulator
The accumulator closely relates to ALU operations. It is
also mapped to location 05H of the data memory and is
capable of carrying out immediate data operations. Data
movement between two data memory locations has to
pass through the accumulator.
Arithmetic and Logic Unit - ALU
This circuit performs 8-bit arithmetic and logic operation.
The ALU provides the following functions.
The ALU not only saves the results of a data operation but
also changes the contents of the status register.
Status Register - STATUS
This 8-bit status register (0AH) contains the zero flag
(Z), carry flag (C), auxiliary carry flag (AC), overflow flag
(OV), power down flag (PDF) and watchdog time-out
flag (TO). It also records the status information and con-
trols the operation sequence.
With the exception of the TO and PDF flags, bits in the
status register can be altered by instructions like most
other register. Any data written into the status register
will not change the TO or PDF flags. In addition it should
be noted that operations related to the status register
may give different results from those intended. The TO
and PDF flags can only be changed by the Watchdog
Timer overflow, chip power-up, clearing the Watchdog
Timer and executing the HALT instruction.
The Z, OV, AC and C flags generally reflect the status of
the latest operations.
In addition, on executing the subroutine call, the status
register will not be automatically pushed onto the stack.
If the contents of the status are important and if the sub-
routine can corrupt the status register, precautions must
be taken to save it properly.
Arithmetic operations (ADD, ADC, SUB, SBC, DAA)
Logic operations (AND, OR, XOR, CPL)
Rotation (RL, RR, RLC, RRC)
Increment and Decrement (INC, DEC)
Branch decision (SZ, SNZ, SIZ, SDZ ....)
HT48RA0-1/HT48CA0-1
December 21, 2005