HT45F0057 datasheet(22/88 Pages) HOLTEK

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HT45F0057

Induction Cooker Flash MCU

HT45F0057

Induction Cooker Flash MCU

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 “CLR WDT” or “HALT” instruction. The PDF flag is affected only by executing

the “HALT” or “CLR WDT” instruction or during a system power-up.

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

• 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 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 is cleared by a system power-up or executing the “CLR WDT” instruction. PDF is set by

executing the “HALT” instruction.

• TO is cleared by a system power-up or executing the “CLR WDT” or “HALT” instruction. TO is

set by a WDT time-out.

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 subroutine can corrupt 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.

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