HT45F43 datasheet(31/152 Pages) HOLTEK

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instruction has been executed. Note that the lower order table data byte is transferred to a user defined

location.

Status Register

- STATUS

This 8-bit register 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). These arithmetic/logical operation

and system management flags are used to record the status and operation of the microcontroller.

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, operations related to the status register may give different results due to the different

instruction operations. The TO flag can be affected only by a system power-up, a WDT time-out or by

executing the

²CLR WDT² or ²HALT² instruction. The PDF flag is affected only by executing 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, on entering an interrupt sequence or executing a subroutine call, the status register will not

be pushed onto the stack automatically. If the contents of the status registers are important and if the

interrupt routine can change the status register, precautions must be taken to correctly save it. Note that

bits 0~3 of the STATUS register are both readable and writeable bits.

STATUS Register

Bit

76543210

Name

¾¾

PDF

R/W

¾¾

R/W

POR

¾¾

xxxx

²x² unknown

Bit 7, 6

Unimplemented, read as

²0²

Bit 5

TO: Watchdog Time-Out flag

0: After power up or executing the

²CLR WDT² or ²HALT² instruction

1: A watchdog time-out occurred.

Bit 4

PDF: Power down flag

0: After power up or executing the

²CLR WDT² instruction

1: By executing the

²HALT² instruction

Bit 3

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

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

Bit 1

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.

HT45F23/HT45F43

8-Bit Flash MCU with Op Amps & Comparators

Rev. 1.20

September 15, 2011

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