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HT46R652-100

A/D with LCD Type 8-Bit OTP MCU

Holtek Semiconductor 

HT46R652

Timer/Event Counter

Two timer/event counters, Timer/Event Counter 0 and

Timer/Event Counter,1 are implemented within the

microcontroller. Timer/Event Counter 0 is a 16-bit pro-

grammable count-up counter whose clock may come

from an external or internal source. The internal clock

source will come from fSYS. Timer/Event Counter 1 is

also a 16-bit programmable count-up counter whose

clock may come from an external source or an internal

source. The internal clock source comes from fSYS/4 or

a 32768Hz source, selected by a configuration option.

The external clock input allows the user to count exter-

nal events, measure time intervals or pulse widths, or to

generate an accurate time base.

There are three registers associated with Timer/Event

Counter 0; TMR0H, TMR0L and TMR0C, and another

three for Timer/Event Counter 1; TMR1H, TMR1L and

TMR1C. Writing to TMR0L and TMR1L will only put the

written data into an internal lower-order byte buffer

(8-bit) while writing to TMR0H and TMR1H will transfer

the specified data and the contents of the lower-order

byte buffer to the TMR0H/TMR1H and TMR0L/TMR1L

registers. The Timer/Event Counter 0/1 preload register

is changed with each TMR0H/TMR1H write operations.

Reading TMR0H/TMR1H will latch the contents of

TMR0H/TMR1H and TMR0L/TMR1L counters to the

destination and the lower-order byte buffer, respectively.

Reading TMR0L/TMR1L will only read the contents of

the lower-order byte buffer. The TMR0C and TMR1C

registers are the Timer/Event Counter control registers,

which control the operating mode, the timer enable or

disable and the active edge type.

The T0M0, T0M1 and T1M0, T1M1 bits define the timer

operational mode. The event count mode is used to

count external events, which requires that the clock

source comes from an external TMR0 or TMR1 pin. The

timer mode functions as a normal timer with the clock

source coming from the internally selected clock source.

The pulse width measurement mode can be used to

count the high or low level duration of an external signal

on pin TMR0 or TMR1, with the count value based on

the internally selected clock source.

In the event count or timer mode, the timer/event coun-

ter starts counting from the current contents in the

fS Y S

8 - s ta g e P r e s c a le r

fIN T

8 -1 M U X

T0P S C 2~T0P S C 0 TM R 0

T0M 1

T0M 0

T0E

L o w B y te

B u ffe r

1 6 - B it

P r e lo a d R e g is te r

D a ta B u s

R e lo a d

T0M 1

T0M 0

T0O N

P u ls e W id th

M e a s u re m e n t

M o d e C o n tro l

H ig h B y te L o w B y te

1 6 - B it T im e r /E v e n t C o u n te r

PFD 0

O v e r flo w to In te r r u p t

Timer/Event Counter 0

D a ta B u s

fS Y S /4

M

U

32768H z X

T1S

f IN T

TM R 1

T1M 1

T1M 0

T1E

L o w B y te

B u ffe r

1 6 - B it

P r e lo a d R e g is te r

R e lo a d

T1M 1

T1M 0

T1O N

P u ls e W id th

M e a s u re m e n t

M o d e C o n tro l

H ig h B y te L o w B y te

1 6 - B it T im e r /E v e n t C o u n te r

PFD 1

Timer/Event Counter 1

O v e r flo w to In te r r u p t

PFD 0

PFD 1

M

U

1 /2

PFD

X

P A 3 D a ta C T R L

P F D S o u r c e O p tio n

PFD Source Option

Rev. 1.00

18

December 19, 2006

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