AT89LP428-20MU ATMEL [ATMEL Corporation], AT89LP428-20MU Datasheet - Page 44

• Manufacturer Part Number: AT89LP428-20MU
• Description: 8-bit Microcontroller with 4K/8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

11.4
44
Mode 3 – 8-bit Split Timer
AT89LP428/828
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
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.
INT0 Pin
Figure
GATE
T0 Pin
11-4. TL0 uses the Timer 0 control bits: C/T, GATE, TR0, INT0, and TF0. TH0 is
÷TPS
÷TPS
C/T = 0
C/T =1
Control
Control
(8 Bits)
(8 Bits)
Interrupt
Interrupt
3654A–MICRO–8/09