HTG2190 datasheet(22/50 Pages) HOLTEK

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HTG2190

Rev. 1.20

July 5, 2002

Timer/Event Counter 0/1

Two timer/event counters are implemented in the

HTG2190. The Timer/Event Counter 0 and 1 contain

16-bit programmable count-up counters whose clock

may come from an external source or the system clock

divided by 4. It should be noted that, if the Timer/Event

Counter 0 is selected, the TMR0 pin should be enabled

by mask option. The pull-high resistor can be disabled

or enabled by software instruction.

Using the internal instruction clock, there is only one ref-

erence time-base. The external clock input allows the

user to count external events, measure time intervals or

pulse width, or to generate an accurate time base.

There are three registers related to Timer/Event Coun-

ter 0; TMR0H (0CH), TMR0L (0DH), TMR0C (0EH).

Writing to TMR0L only writes the data into a low byte

buffer. Writing to TMR0H will write the data and the con-

tents of the low byte buffer into the Timer/Event Counter

0 preload register (16-bit) simultaneously. The

Timer/Event Counter 0 preload register is changed only

by a write to TMR0H operation. Writing to TMR0L will

keep the Timer/Event Counter 0 preload register un-

changed.

Reading TMR0H will also latch the TMR0L into the low

byte buffer to avoid false timing problems. Reading the

TMR0L only returns the value from the low byte buffer

which may be a previously loaded value. In other words,

the low byte of Timer/Event Counter 0 cannot be read di-

S y s t e m C l o c k / 4

T M 1

T M 0

T M R 0

T M R 1

T E

T M 1

T M 0

T O N

P u l s e W i d t h

M e a s u r e m e n t

M o d e C o n t r o l

T i m e r / E v e n t C o u n t e r 0 / 1

P r e l o a d R e g i s t e r

T i m e r / E v e n t

C o u n t e r 0 / 1

L o w B y t e

B u f f e r

D a t a B u s

R e l o a d

O v e r f l o w

t o I n t e r r u p t

Timer/Event Counter 0/1

Label

Bits

Function

0~2

Unused bit, read as

²0²

Defines the TMR0/TMR1 active edge of timer/event counter

(0=active on low to high; 1=active on high to low)

TON

Enable/disable timer counting

(0=disabled; 1=enabled)

Unused bit, read as

²0²

TM1, TM0

7, 6

Define the operating mode (TM1, TM0)

01=Event count mode (external clock)

10=Timer mode (internal clock)

11=Unused

00=Unused

TMR0C/TMR1C register

Label

Bits

Function

FAST

0=speed-up 32K x'tal (default)

1=Non-speed-up 32K x'tal

RTF

Select the R-to-F function

0=disable R-to-F (default), 1=enable R-to-F

RTMR0

Select the TMR0 pull-high resistor (1=with pull-high; 0=without pull-high)

RTMR1

Select the TMR1 pull-high resistor (1=with pull-high; 0=without pull-high)

VDET

Supply voltage detection circuit (1=enable VDET, 0=disable VDET)

5~7

Unused bit, read as

²0²

X'TALC register

HTG2190 Datasheet(PDF) 22 Page - Holtek Semiconductor Inc

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