AT89LP51 datasheet(48/113 Pages) ATMEL

48 / 113 page

3709C–MICRO–5/11

AT89LP51/52 - Preliminary

11.3

Mode 2 – 8-bit Auto-Reload Timer/Counter

Mode 2 configures the Timer register as an 8-bit Counter (TL1) with automatic reload, as shown

in Figure 11-3. Overflow from TL1 not only sets TF1, but also reloads TL1 with the contents of

TH1, which is preset by software. The reload leaves TH1 unchanged. Mode 2 operation is the

same for Timer/Counter 0.

Figure 11-3. Timer/Counter 1 Mode 2: 8-bit Auto-Reload

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, GATE0, 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

AT89LP51/52 can appear to have four 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

Mode 2:

Time-out Period

256

TH0

–

()

System Frequency

--------------------------------------------------

TPS

()

OSC

T1 Pin

TR1

GATE1

TF1

TL1

(8 Bits)

TH1

(8 Bits)

Control

Reload

Interrupt

INT0 Pin

C/T = 0

C/T = 1

÷CDV

÷TPS

Control

Interrupt

Control

Interrupt

(8 Bits)

C/T = 0

C/T =1

T0 Pin

GATE0

INT0 Pin

÷TPS

÷CDV

OSC

÷CDV

OSC

AT89LP51 数据表(PDF) 48 Page - ATMEL Corporation

AT89LP51 数据表(HTML) 48 Page - ATMEL Corporation

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

数据表下载

链接网址

AT89LP51 数据表(PDF) 48 Page - ATMEL Corporation

AT89LP51 数据表(HTML) 48 Page - ATMEL Corporation

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

数据表 下载

链接网址

数据表下载