HT45R34 datasheet(15/41 Pages) HOLTEK

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HT45R34

Rev. 1.20

October 15, 2007

Bit No.

Label

Function

0~2

Unused bit, read as

²0²

Undefined bit, this bit can read/write

RCOCON Enable or disable external RC oscillation converter counting (0= disabled; 1= enabled)

RCOM0

RCOM1

RCOM2

Define the Timer A clock source, RCOM2, RCOM1, RCOM0=

000= System clock

001= System clock/4

010= Unused

011= Unused

100= Unused

101= Unused

110= Unused

111= Unused

RCOCCR (22H) Register

of Timer A/Timer B can not be read directly. It must read

TMRAH/TMRBH first to ensure that the low byte con-

tents of Timer A/Timer B are latched into the buffer.

The resistor and capacitor form an oscillation circuit and

input to TMRBH and TMRBL. The RCOM0, RCOM1

and RCOM2 bits of RCOCCR define the clock source of

Timer A. It is recommended that the clock source of

Timer A uses the system clock or the instruction clock.

If the RCOCON bit, bit 4 of RCOCCR, is set to

²1², Timer

A and Timer B will start counting until Timer A or Timer B

overflows, the timer/event counter will then generate an

interrupt request flag which is RCOCF; bit 4 of INTC1.

The Timer A and Timer B will stop counting and will reset

the RCOCON bit to

²0² at the same time. If the

RCOCON bit is

²1², TMRAH, TMRAL, TMRBH and

TMRBL cannot be read or written.

Bit No.

Label

Function

OVB

In the RC oscillation converter mode, this bit is used to define the timer/event counter interrupt,

which comes from Timer A overflow or Timer B overflow.

(0= Timer A overflow; 1= Timer B overflow)

RCO

Define RC oscillation converter mode.

(0= Disable RC oscillation converter mode; 1= Enable RC oscillation converter mode)

2~3

Unused bit, read as

²0²

4~7

4-bit read/write registers for user defined.

RCOCR (25H) Register

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