AT89C5132-ROTIL datasheet(52/182 Pages) ATMEL

52 / 182 page

4173E–USB–09/07

AT89C5132

Counter. TL0 uses the Timer 0 control Bits C/T0# and GATE0 in TMOD register, and TR0 and

TF0 in TCON register in the normal manner. TH0 is locked into a Timer function (counting

FTF1/6) and takes over use of the Timer 1 interrupt (TF1) and run control (TR1) Bits. Thus, oper-

ation of Timer 1 is restricted when Timer 0 is in mode 3. Figure 12-7 gives the autoreload period

calculation formulas for both TF0 and TF1 flags.

Figure 12-8. Timer/Counter 0 in Mode 3: Two 8-bit Counters

Figure 12-9. Mode 3 Overflow Period Formula

12.4

Timer 1

Timer 1 is identical to Timer 0 excepted for Mode 3 which is a hold-count mode. Following com-

ments help to understand the differences:

•

Timer 1 functions as either a Timer or event Counter in three modes of operation. Figure 12-

2 through Figure 12-6 show the logical configuration for modes 0, 1, and 2. Timer 1’s mode

3 is a hold-count mode.

•

Timer 1 is controlled by the four high-order Bits of TMOD register (see Table 41) and Bits 2,

3, 6 and 7 of TCON register (see Figure 40). TMOD register selects the method of Timer

gating (GATE1), Timer or Counter operation (C/T1#) and mode of operation (M11 and M01).

TCON register provides Timer 1 control functions: overflow flag (TF1), run control bit (TR1),

interrupt flag (IE1) and interrupt type control bit (IT1).

•

Timer 1 can serve as the Baud Rate Generator for the Serial Port. Mode 2 is best suited for

this purpose.

•

For normal Timer operation (GATE1 = 0), setting TR1 allows TL1 to be incremented by the

selected input. Setting GATE1 and TR1 allows external pin INT1 to control Timer operation.

•

Timer 1 overflow (count rolls over from all 1s to all 0s) sets the TF1 flag generating an

interrupt request.

•

When Timer 0 is in mode 3, it uses Timer 1’s overflow flag (TF1) and run control bit (TR1).

For this situation, use Timer 1 only for applications that do not require an interrupt (such as a

Baud Rate Generator for the Serial Port) and switch Timer 1 in and out of mode 3 to turn it

off and on.

•

It is important to stop the Timer/Counter before changing modes.

TR0

TCON.4

TF0

TCON.5

INT0

GATE0

TMOD.3

Overflow

Timer 0

Interrupt

Request

C/T0#

TMOD.2

TL0

(8 Bits)

TR1

TCON.6

TH0

(8 Bits)

TF1

TCON.7

Overflow

Timer 1

Interrupt

Request

TIM0

CLOCK

TIM0

CLOCK

TF0

PER =

FTIM0

⋅ (256 – TL0)

TF1

PER =

TIM0

⋅ (256 – TH0)

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