HT46R064B/065B/066B
·
STATUS Register
Bit
7
6
5
TO
R
4
PDF
R
3
OV
R/W
x
2
Z
1
AC
R/W
x
0
Name
R/W
C
¾
¾
¾
¾
¾
¾
R/W
x
R/W
x
POR
0
0
²x² unknown
Bit 7, 6
Unimplemented, read as ²0²
TO: Watchdog Time-Out flag
Bit 5
Bit 4
Bit 3
0: After power up or executing the ²CLR WDT² or ²HALT² instruction
1: A watchdog time-out occurred.
PDF: Power down flag
0: After power up or executing the ²CLR WDT² instruction
1: By executing the ²HALT² 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
highest-order bit or vice versa.
Bit 2
Bit 1
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
Bit 0
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
during a subtraction operation
C is also affected by a rotate through carry instruction.
Input/Output Ports and Control Registers
high, for an output it must be set low. During program in-
itialisation, it is important to first setup the control regis-
ters to specify which pins are outputs and which are
inputs before reading data from or writing data to the I/O
ports. One flexible feature of these registers is the ability
to directly program single bits using the ²SET [m].i² and
²CLR [m].i² instructions. The ability to change I/O pins
from output to input and vice versa by manipulating spe-
cific bits of the I/O control registers during normal pro-
gram operation is a useful feature of these devices.
Within the area of Special Function Registers, the port
PA, PB, etc data I/O registers and their associated con-
trol register PAC, PBC, etc play a prominent role. These
registers are mapped to specific addresses within the
Data Memory as shown in the Data Memory table. The
data I/O registers, are used to transfer the appropriate
output or input data on the port. The control registers
specifies which pins of the port are set as inputs and
which are set as outputs. To setup a pin as an input, the
corresponding bit of the control register must be set
Rev. 1.00
24
April 8, 2011
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
