HT48RA0-5 Holtek Semiconductor, HT48RA0-5 Datasheet - Page 7

• Manufacturer Part Number: HT48RA0-5
• Description: Remote Type 8-Bit OTP MCU
• Manufacturer: Holtek Semiconductor

Rev.1.00
Bit No.
6~7
0
1
2
3
4
5
Label
PDF
OV
AC
TO
C
Z
RAM Mapping
C is set if the operation results in a carry during an addition operation or if a borrow does not
take place during a subtraction operation; otherwise C is cleared. C is also affected by a ro-
tate through carry instruction.
AC is set if the operation results in a carry out of the low nibbles in addition or no borrow from
the high nibble into the low nibble in subtraction; otherwise AC is cleared.
Z is set if the result of an arithmetic or logic operation is zero; otherwise Z is cleared.
OV is set if the operation results in a carry into the highest-order bit but not a carry out of the
highest-order bit, or vice versa; otherwise OV is cleared.
PDF is cleared when either a system power-up or executing the CLR WDT instruction. PDF
is set by executing the HALT instruction.
TO is cleared by a system power-up or executing the CLR WDT or HALT instruction. TO is
set by a WDT time-out.
Unused bit, read as 0
Status (0AH) Register
7
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, the other
status register bits can be altered by instructions like
most other register. Any data written into the status regis-
ter will not change the TO or PDF flags. In addition it
should be noted that operations related to the status reg-
ister may give different results from those intended. The
TO and PDF flags can only be changed by the Watchdog
Timer overflow, device 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.
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 ....)
Function
HT48RA0-5
March 23, 2010
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