ht82k68e Holtek Semiconductor Inc., ht82k68e Datasheet - Page 8

• Manufacturer Part Number: ht82k68e
• Description: Ht82k68e -- Multimedia Keyboard Encoder 8-bit Otp Mcu
• Manufacturer: Holtek Semiconductor Inc.

(INTC;0BH), the timer counter register (TMR;0DH), the
timer counter control register (TMRC;0EH), the I/O regis-
ters (PA;12H, PB;14H, PC;16H, PD;18H, PE;1AH) and
the I/O control registers (PAC;13H, PBC;15H, PCC;17H,
PDC;19H, PEC;1BH). The remaining space before the
60H is reserved for future expanded usage and reading
these locations will get the result 00H. The general pur-
pose data memory, addressed from 60H to FFH, is used
for data and control information under instruction com-
mand.
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 registers
(MP0;01H, MP1;03H).
Indirect Addressing Register
Location 00H and 02H are indirect addressing registers
that are not physically implemented. Any read/write op-
eration of [00H] and [02H] can access the data memory
Rev. 2.00
RAM Mapping
8
pointed to by MP0 (01H) and MP1 (03H) respectively.
Reading location 00H or 02H indirectly will return the re-
sult 00H. Writing indirectly results in no operation.
The function of data movement between two indirect ad-
dressing registers is not supported. The memory pointer
registers, MP0 and MP1, are 8-bit registers which can
be used to access the data memory by combining corre-
sponding indirect addressing registers.
Accumulator
The accumulator is closely related to the ALU opera-
tions. It is also mapped to location 05H of the data mem-
ory and is capable of carrying 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 operation.
The ALU provides the following functions:
The ALU not only saves the results of a data operation but
also changes the status register.
Status Register - Status
The 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 watch dog time-out
flag (TO). The status register not only records the status
information but also 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 flags. 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 system power up, Watch-
dog Timer overflow, executing the HALT instruction and
clearing the Watchdog Timer.
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 auto-
matically pushed onto the stack. If the contents of status
are important and if the subroutine can corrupt the sta-
tus register, precaution must be taken to save it prop-
erly.
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 ....)
HT82K68E
July 10, 2007