HT48R02M Holtek Semiconductor, HT48R02M Datasheet - Page 15

• Manufacturer Part Number: HT48R02M
• Description: (HT4xR0xM) 1.5V Battery 8-Bit OTP MCU
• Manufacturer: Holtek Semiconductor

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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.
Status Register - STATUS
This 8-bit register 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).
These arithmetic/logical operation and system manage-
ment flags are used to record the status and operation of
the microcontroller.
Rev. 1.00
STATUS Register
Bit 7, 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Name
POR
R/W
Bit
Unimplemented, read as 0
TO: Watchdog Time-Out flag
0: After power up or executing the CLR WDT or HALT instruction
1: A watchdog time-out occurred.
PDF: Power down flag
0: After power up or executing the CLR WDT instruction
1: By executing the HALT instruction
OV: Overflow flag
0: no overflow
1: an operation results in a carry into the highest-order bit but not a carry out of the
Z: Zero flag
0: The result of an arithmetic or logical operation is not zero
1: The result of an arithmetic or logical operation is zero
AC: Auxiliary flag
0: no auxiliary carry
1: an 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
C: Carry flag
0: no carry-out
1: an operation results in a carry during an addition operation or if a borrow does not take place
C is also affected by a rotate through carry instruction.
7
during a subtraction operation
highest-order bit or vice versa.
6
HT46R01M/HT46R02M/HT48R01M/HT48R02M
TO
R
5
0
PDF
15
R
4
0
With the exception of the TO and PDF flags, bits in the
status register can be altered by instructions like most
other registers. Any data written into the status register
will not change the TO or PDF flag. In addition, opera-
tions related to the status register may give different re-
sults due to the different instruction operations. The TO
flag can be affected only by a system power-up, a WDT
time-out or by executing the CLR WDT or HALT in-
struction. The PDF flag is affected only by executing the
power-up.
The Z, OV, AC and C flags generally reflect the status of
the latest operations.
In addition, on entering an interrupt sequence or execut-
ing a subroutine call, the status register will not be
pushed onto the stack automatically. If the contents of
the status registers are important and if the interrupt rou-
tine can change the status register, precautions must be
taken to correctly save it. Note that bits 0~3 of the
STATUS register are both readable and writeable bits.
HALT or CLR WDT instruction or during a system
R/W
OV
3
x
R/W
Z
2
x
R/W
AC
1
x
December 18, 2009
x unknown
R/W
C
0
x