HT95R23 datasheet(34/53 Pages) HOLTEK

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HT95R23

Rev. 1.00

March 25, 2008

Programmable Frequency Divider (PFD) Generator

- MUSIC

A Programmable Frequency Divider function, otherwise known as PFD, is integrated within the microcontroller, provid-

ing a means of accurate frequency generation. It is composed of two functional blocks: a prescaler and a general coun-

ter.

PFD Control Register

The overall PFD function is controlled using the PFDD register. The prescaler is controlled by the register bits, PRES0

and PRES1. The general counter is programmed by an 8-bit register PFDD. The clock source for the PFD can be se-

lected to be either the 3.58MHz/4 or the 32768Hz oscillator. To enable the PFD output, the PFDEN bit should be set to

1. When the PFD is disabled the PFDD register is inhibited to be written to. To modify the PFDD contents, the PFD must

be enabled. When the generator is disabled, the PFDD is cleared by hardware.

PFD Data Register

Bit No.

Label

R/W

Function

7~0

PFD data register

PFDD (2FH) Register

PFD_Output_Frequency=

Prescaler_Output

2x(N 1)

, where N = the value of the PFD Data

RTC Function

When RTC 1000ms time-out occurs, the hardware will set the interrupt request flag RTCF and the RTCTO flag to 1.

When the interrupt service routine is serviced, the interrupt request flag (RTCF) will be cleared to 0, but the flag RTCTO

remains in its original values. This bit (RTCTO) should be cleared only by software. However, next RTC interrupt will

still occur, even though the RTCTO flag is not cleared.

P r e s c a l e r

O u t p u t

P F D D

P R E S 1 , P R E S 0

3 2 7 6 8 H z

3 . 5 8 M H z / 4

P F D E N

P F D

O u t p u t

M U S I C

B u z z e r

P F D D

b 0

N o t i m p l e m e n t e d , r e a d a s " 0 "

b 7

P F D O u t p u t E n a b l e

1 : e n a b l e

0 : d i s a b l e

P F D P r e s c a l e r S e l e c t

0 0 : P r e s c a l e r o u t p u t = P F D f r e q u e n c y s o u r c e / 1

0 1 : P r e s c a l e r o u t p u t = P F D f r e q u e n c y s o u r c e / 2

1 0 : P r e s c a l e r o u t p u t = P F D f r e q u e n c y s o u r c e / 4

1 1 : P r e s c a l e r o u t p u t = P F D f r e q u e n c y s o u r c e / 8

P F D F r e q u e n c y S o u r c e S e l e c t

1 : 3 . 5 8 M H z / 4

0 : 3 2 7 6 8 H z

F P F D

P R E S 1 P R E S 0 P F D E N

R T C C

b 0

N o t i m p l e m e n t e d , r e a d a s " 0 "

b 7

R T C F u n c t i o n E n a b l e

1 : e n a b l e

0 : d i s a b l e

R T C T i m e - o u t F l a g

1 : R T C t i m e - o u t o c c u r s

0 : R T C t i m e - o u t d o e s n o t o c c u r

R T C E N

N o t i m p l e m e n t e d , r e a d a s " 0 "

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