EM6580 datasheet(13/56 Pages) EMMICRO

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EM6580

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5.2 Special 4 stage Frequency Divider

If an internal RC clock or external frequency higher than 32 kHz or 50 kHz is selected, then the special 4 stage

Frequency Divider must be used to select a frequency close to 32 kHz or 50 kHz for the SysClk - system clock

used by the Prescaler. This is done by register option.(Refer to RegMFP1 table chapter

95H

14.8)

If the external clock will be used, the same register option used to select the division for SysClk. Table below

shows recommended divisions in this 4 stage divider.

Table 5.2.1 PA[1] I/O status depending on its RegPACntl3 and RegPa0OE registers

RC frequency

Ext. clock

(1)base

(2) base

RC frequency or External freq.

MUST be divided by

Typical Obtained SysClk

Min.- typ. If RC - Max. [kHz]

10 kHz – 50 kHz

No Division to SysClk

10 – 32 – 50

55 kHz – 100 kHz

100

Divided by 2

27.5 – 32 – 50

110 kHz – 200 kHz

128

200

Divided by 4

27.5 – 32 – 50

220 kHz – 400 kHz

256

400

Divided by 8

27.5 – 32 – 50

400 kHz – 1 MHz

500

800

Divided by 16

10 – 32 – 62.5

5.3 Prescaler

The prescaler consists of a fifteen element divider chain which delivers clock signals for the peripheral circuits

such as timer/counter, debouncer and edge detectors, as well as generating prescaler interrupts. The input to

the prescaler is the system clock signal closest to 32 kHz or 50 kHz which comes from the RC oscillator or

external clock as divided by the preceding divider. Power on initializes the prescaler to Hex(0001).

Table 5.3.1 Prescaler Clock Name Definition

Function

Name

32 KHz

SysClk

50 KHz

SysClk

Function

Name

32 KHz

SysClk

50 KHz

SysClk

System clock

Ck[16]

32768 Hz

50000 Hz

System clock / 256

Ck[8]

128 Hz

195 Hz

System clock / 2

Ck[15]

16384 Hz

25000 Hz

System clock / 512

Ck[7]

64 Hz

97 Hz

System clock / 4

Ck[14]

8192 Hz

12500 Hz

System clock / 1024

Ck[6]

32 Hz

49 Hz

System clock / 8

Ck[13]

4096 Hz

6250 Hz

System clock / 2048

Ck[5]

16 Hz

24 Hz

System clock/ 16

Ck[12]

2048 Hz

3125 Hz

System clock / 4096

Ck[4]

8 Hz

12 Hz

System clock / 32

Ck[11]

1024 Hz

1562 Hz

System clock / 8192

Ck[3]

4 Hz

6 Hz

System clock / 64

Ck[10]

512 Hz

781 Hz

System clock / 16384

Ck[2]

2 Hz

3 Hz

System clock / 128

ck [9]

256 Hz

390 Hz

System clock / 32768

Ck[1]

1 Hz

1.5 Hz

Figure 7. Prescaler Frequency Timing

Prescaler Reset

SysClk = System clock Ck[16]

Ck[15]

Ck[14]

Ck[13]

Ck[2]

Ck[1]

Horizontal Scale change

First positive edge of 1 Hz clock Ck[1] is 1 sec after the falling reset edge

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