HT49CV3 datasheet(9/44 Pages) HOLTEK

9 / 44 page

HT49RV3/HT49CV3

Rev. 1.30

March 20, 2007

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

²SET [m].i² and ²CLR

[m].i

². They are also indirectly accessible through mem-

ory 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] accesses the RAM pointed to

by MP0 (01H) and MP1(03H), respectively. Reading lo-

cation 00H or 02H indirectly returns the result 00H. Writ-

ing indirectly leads to no operation.

The function of data movement between two indirect ad-

dressing registers is not supported. The memory pointer

registers, MP0 and MP1, are both 8-bit registers used to

access the RAM by combining corresponding indirect

addressing registers. MP0 can only be applied to data

memory, while MP1 can be applied to data memory and

VFD display memory.

Accumulator

- ACC

The Accumulator (ACC) is closely related with opera-

tions carried out by the ALU. It is mapped to location

05H of the RAM and is capable of operating with imme-

diate data. The data movement between two data mem-

ory locations must pass through the ACC.

Arithmetic and Logic Unit

- ALU

This circuit performs 8-bit arithmetic and logic opera-

tions and 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 etc.)

The ALU not only saves the results of a data operation

but also changes the status register.

Status Register

- STATUS

The status register (0AH) is 8 bits wide and contains a

carry flag (C), an auxiliary carry flag (AC), a zero flag (Z),

an overflow flag (OV), a power down flag (PDF), and a

watchdog time-out flag (TO). It also records the status

information and controls the operation sequence.

Except for the TO and PDF flags, bits in the status reg-

ister can be altered by instructions similar to other reg-

isters. Data written into the status register does not alter

the TO or PDF flags. Operations related to the status

intended. The TO and PDF flags can only be changed

by a Watchdog Timer overflow, chip power-up, or clear-

ing the Watchdog Timer and executing a

²HALT² in-

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

the latest operations.

On entering an interrupt sequence or executing a sub-

routine call, the status register will not be automatically

pushed onto the stack. If the contents of the status is im-

portant, and if the subroutine is likely to corrupt the sta-

tus register, the programmer should take precautions

and save it properly.

Interrupts

The HT49RV3/HT49CV3 provides two external inter-

rupts, two internal timer/event counter interrupts, three

remote control timer interrupts, an internal real time

clock interrupt and serial interface interrupt. The

Interrupt Control Register 0 (INTC0;0BH) and Interrupt

Control Register 1 (INTC1;1EH) both contain the inter-

rupt control bits that are used to set the enable/disable

status and interrupt request flags.

Bit No.

Label

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.

1AC

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 logic operation is zero, otherwise Z is cleared.

3OV

OV is set if an operation results in a carry into the highest-order bit but not a carry out of

the highest-order bit, or vice versa, otherwise OV is cleared.

PDF

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

²CLR WDT² instruction.

PDF is set by executing the

²HALT² instruction.

5TO

TO is cleared by a 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 (0AH) Register

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