AT89LP428 datasheet(44/149 Pages) ATMEL

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3654A–MICRO–8/09

AT89LP428/828

11.4

Mode 3 – 8-bit Split Timer

Timer 1 in Mode 3 simply holds its count. The effect is the same as setting TR1 = 0. Timer 0 in

Mode 3 establishes TL0 and TH0 as two separate counters. The logic for Mode 3 on Timer 0 is

shown in Figure 11-4. TL0 uses the Timer 0 control bits: C/T, GATE, TR0, INT0, and TF0. TH0 is

locked into a timer function (counting clock cycles) and takes over the use of TR1 and TF1 from

Timer 1. Thus, TH0 now controls the Timer 1 interrupt. While Timer 0 is in Mode 3, Timer 1 will

still obey its settings in TMOD but cannot generate an interrupt.

Mode 3 is for applications requiring an extra 8-bit timer or counter. With Timer 0 in Mode 3, the

AT89LP428/828 can appear to have three Timer/Counters. When Timer 0 is in Mode 3, Timer 1

can be turned on and off by switching it out of and into its own Mode 3. In this case, Timer 1 can

still be used by the serial port as a baud rate generator or in any application not requiring an

interrupt.

Figure 11-4. Timer/Counter 0 Mode 3: Two 8-bit Counters

Note:

RH0/RL0 are not required by Timer 0 during Mode 3 and may be used as temporary storage

registers.

Control

Interrupt

Control

Interrupt

(8 Bits)

C/T = 0

C/T =1

T0 Pin

GATE

INT0 Pin

÷TPS

AT89LP428 数据表(PDF) 44 Page - ATMEL Corporation