HT46C63 datasheet(11/44 Pages) HOLTEK

11 / 44 page

HT46R63/HT46C63

Rev. 1.90

May 17, 2004

Bank Pointer

The bank pointer is used to assign the accessed RAM

bank. When the users want to access the RAM bank

²0²

a 0 should be loaded onto BP. When the BP is equal to

²1², the LCD RAM will be accessed (use MP1/R1 indi-

rect addressing only). RAM locations before 40H in any

bank are overlapped.

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:

· 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 ....)

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

tion operations related to the status register may give

different results from those intended. The TO flag

can be affected only by system power-up, a WDT

time-out or executing the

²CLR WDT² or ²HALT² in-

struction. The PDF flag can be affected only by exe-

cuting the

²HALT² or ²CLR WDT² instruction or a

system power-up.

The Z, OV, AC and C flags generally reflect the status of

the latest operations.

In addition, on entering the interrupt sequence or exe-

cuting the subroutine call, the status register will not be

pushed onto the stack automatically. 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.

Interrupt

The microcontroller provides two external interrupts, an

internal timer/event counter overflow interrupt, a time

base time-out interrupt, an A/D converter

end-of-conversion interrupt and a real time clock

time-out interrupt. The interrupt control registers

(INTC0: 0BH and INTC1: 1EH) contains the interrupt

control bits to set the enable or disable and the interrupt

request flags.

Once an interrupt subroutine is serviced, all the other in-

terrupts will be blocked (by clearing EMI bit). This

scheme may prevent any further interrupt nesting. Other

interrupt requests may happen during this interval but

only the interrupt request flags are recorded. If a certain

interrupt requires servicing within the service routine,

the programmer may set the EMI and the corresponding

bit of INTC0/INTC1 to allow interrupt nesting. If the stack

is full, the interrupt request will not be acknowledged,

even if the related interrupt is enabled, until the SP is de-

creased. If immediate service is desired, the stack has

to be prevented from becoming full.

Labels

Bits

Function

C is set if an 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 rotate through

carry instruction.

AC is set if 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; otherwise AC is cleared.

Z is set if the result of an arithmetic or logical 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 high-

est-order bit, or vice versa; otherwise OV is cleared.

PDF

PDF is cleared by a system power-up or executing the

²CLR WDT² instruction. PDF is set by exe-

cuting the

²HALT² instruction.

TO is cleared by system power-up or executing the

²CLR WDT² or ²HALT² instruction. TO is set

by a WDT time-out.

6, 7

Unused bit, read as

²0²

Status Register

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