SH79F6488PSLASH080PR datasheet(57/152 Pages) SINOWEALTH

57 / 152 page

SH79F6488/SH79F6489

7.8.3 Timer3

Timer3 is a 16-bit auto-reload timer. It is implemented as a 16-bit register accessed as two cascaded Data Registers: TH3 and

TL3. It is controlled by the T3CON register. The Timer3 interrupt can be enabled by setting ET3 bit in IEN0 register (Refer to

Interrupt Section for details).

Timer3 has only one operating mode: 16-bit Counter/Timer with auto-reload. Timer3 also supports the following features:

selectable pre-scaler setting and Operation during CPU Power-Down mode.

Timer3 consists of a 16-bit counter/reload register (TH3, TL3). When writing to TH3 and TL3, they are used as timer load

register. When reading from TH3 and TL3, they are used as timer counter register. Setting the TR3 bit enables Timer 3 to count

up. The Timer will overflow from 0xFFFF to 0x0000 and set the TF3 bit. This overflow also causes the 16-bit value written in

timer load register to be reloaded into the timer counter register. Writing to TH3 also can cause the 16-bit value written in timer

load register to be reloaded into the timer counter register.

Read or write operation to TH3 and TL3 should follow these steps:

Write operation: Low nibble first, High nibble to update the counter

Read operation: High nibble first, Low nibble followed.

TF3

The Block Diagram of Timer3

TL3

TH3

Increment Mode

0:Switch Off

1:Switch On

16-bit Counter

Interrupt

Request

Overflow

Flag

TR3

System Clock

Prescaler

1,8,64,256

T3PS[1:0]

T3CLKS[1:0]

32.768kHz

Crystal

If T3CLKS[1:0] is 00, Timer 3 can’t work in Power Down mode.

If T3CLKS[1:0] is 01,Timer3 can work in Power Down mode. Even close all oscillator, Timer 3 can count.

If T3CLKS[1:0] is 10, Timer3 can work in Power Down mode If low frequency oscillator is off,then Timer3 can not count.

It can be described in the following table.

T3CLKS[1:0]

Oscillator status

Can work in normal mode

Can work in Power Down mode

YES

low frequency off in power-down

YES

low frequency on in power-down

YES

Note:

(1) When TH3 and TL3 read or written, must make sure TR3 = 0.

(2) When T3 is selected as Timer3 clock source and TR3 is set 0 to 1, the first T3 down edge will be ignored.

(3) Low frequency oscillator will keep working when system entering Power-down mode with high frequency oscillator (OSC2).

Low frequency oscillator will turn off when system entering Power-down mode with low frequency oscillator (32.768kHz).

SH79F6488P/080PR Datasheet(PDF) 57 Page - SINOWEALTH Electronic Ltd

SH79F6488P/080PR Datasheet(HTML) 57 Page - SINOWEALTH Electronic Ltd

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL