ht82m9aae Holtek Semiconductor Inc., ht82m9aae Datasheet - Page 9

• Manufacturer Part Number: ht82m9aae
• Description: Usb Mouse Encoder 8-bit Mcu With Eeprom
• Manufacturer: Holtek Semiconductor Inc.

Rev. 1.20
Bank 1 RAM Mapping
9
Accumulator
The accumulator is closely related to ALU operations. It
is also mapped to location 05H of the data memory and
can carry out immediate data operations. The data
movement between two data memory locations must
pass through the accumulator.
Arithmetic and Logic Unit - ALU
This circuit performs 8-bit arithmetic and logic opera-
tions. The ALU provides the following functions:
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The ALU not only saves the results of a data operation
but also changes the status register.
Status Register - STATUS
This 8-bit 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 controls
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 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 from those intended.
The TO flag can be affected only by a system power-up,
a WDT time-out or executing the ²CLR WDT² or ²HALT²
instruction. The PDF flag can be affected only by exe-
cuting the ²HALT² or ²CLR WDT² instruction or during a
system power-up.
The Z, OV, AC and C flags generally reflect the status of
the latest operations.
In addition, upon entering the interrupt sequence or exe-
cuting a subroutine call, the status register will not be
automatically pushed onto the stack. If the contents of
the status are important and if the subroutine can cor-
rupt 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 ....)
HT82M9AEE/HT82M9AAE
August 13, 2007