HT46R0664 datasheet(23/92 Pages) HOLTEK

23 / 92 page

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HT46R0664

Enhanced A/D+LCD 8-Bit OTP MCU

Look-up Table Registers – TBLP, TBLH

These three special function registers are used to control operation of the look-up table which is

stored in the Program Memory. TBLP is the table pointer and indicates the location where the table

data is located. Their value must be setup before any table read commands are executed. Their value

can be changed, for example using the “INC” or “DEC” instructions, allowing for easy table data

pointing and reading. TBLH is the location where the high order byte of the table data is stored

after a table read data 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 “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.

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.

STATUS Register

Bit

Name

—

PDF

�C

R/W

—

R/W

POR

—

“x” �nknown

Bit 7~6

Unimplemented, read as “0”

Bit 5

TO: Watchdog Time-Out flag

0: after power up or executing the “CLR WDT” or “HALT” instruction

1: a watchdog time-out occurred

Bit 4

PDF: Power down flag

0: after power up or executing the “CLR WDT” instruction

1: by executing the “HALT” 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

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