HT46R005 datasheet(35/62 Pages) HOLTEK

35 / 62 page

HT48R005/HT46R005

Rev. 1.00

November 29, 2011

If the CTRL0 register has selected the buzzer function,

then for both buzzer outputs to operate, it is essential

that the Port A control register PAC bit 0 and PAC bit 1

are setup as outputs. If only one pin is setup as an out-

put, the other pin can still be used as a normal data input

pin. However, if both pins are setup as inputs then the

buzzer will not function. The buzzer outputs will only be

activated if bit PA0 is set to

²1². This output data bit is

used as the on/off control bit for the buzzer outputs.

Note that the BZ and BZ outputs will both be low if the

PA0 output data bit is cleared to

²0². The condition of

data bit PA1 has no effect on the overall control of the BZ

and BZ pins.

Using this method of frequency generation, and if a

crystal oscillator is used for the system clock, very pre-

cise values of frequency can be generated.

I/O Interfacing

The Timer/Event Counter, when configured to run in the

event counter or pulse width measurement mode, re-

quires the use of an external timer pin for its operation.

As this pin is a shared pin it must be configured correctly

to ensure that it is setup for use as a Timer/Event Coun-

ter input pin. This is achieved by ensuring that the mode

select bits in the Timer/Event Counter control register,

select either the event counter or pulse width measure-

ment mode. Additionally the corresponding PAC Port

Control Register bit must be set high to ensure that the

pin is setup as an input. Any pull-high resistor connected

to this pin will remain valid even if the pin is used as a

Timer/Event Counter input.

Programming Considerations

When configured to run in the timer mode, the internal

system clock is used as the timer clock source and is

therefore synchronised with the overall operation of the

microcontroller. In this mode when the appropriate timer

nal interrupt signal directing the program flow to the re-

spective internal interrupt vector. For the pulse width

measurement mode, the internal system clock is also

used as the timer clock source but the timer will only run

when the correct logic condition appears on the external

timer input pin. As this is an external event and not syn-

chronized with the internal timer clock, the

microcontroller will only see this external event when the

next timer clock pulse arrives. As a result, there may be

small differences in measured values requiring pro-

grammers to take this into account during programming.

The same applies if the timer is configured to be in the

event counting mode, which again is an external event

and not synchronized with the internal system or timer

clock.

T i m e r O v e r f l o w

B u z z e r C l o c k

P A 0 D a t a

B Z O u t p u t a t P A 0

B Z O u t p u t a t P A 1

Buzzer Function

BZEN1

BZEN0

PAC Register

PAC0

PAC Register

PAC1

PA Register

PA0

PA Register

PA1

Output Function

PA0=BZ, PA1=BZ

PA0=0, PA1=0

PA0=BZ, PA1=input

PA0=0, PA1=input

PA0=input, PA1=D

PA0=input, PA1=input

Note:

The BZEN1 and BZEN0 bits are located in the CTRL0 register;

²I²: Input; ²O²: Output;

²×² don¢t care; ²D²: data ²0² or ²1²; ²C²: CMOS output structure.

PA0/PA1 I/O Funcion Control

HT46R005 Datasheet(PDF) 35 Page - Holtek Semiconductor Inc

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