Electronic Components Datasheet Search
  English  ▼

Delete All
ON OFF


ATmega8A-AU Datasheet(PDF) 39 Page - ATMEL Corporation

Part No. ATmega8A-AU
Description  8-bit with 8K Bytes In-System Programmable Flash
Download  307 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  ATMEL [ATMEL Corporation]
Homepage  http://www.atmel.com
Logo 

 39 page
background image
39
8159C–AVR–07/09
ATmega8A
Figure 10-3. MCU Start-up, RESET Extended Externally
10.2.2
External Reset
An External Reset is generated by a low level on the RESET pin. Reset pulses longer than the
minimum pulse width (see Table 25-3 on page 247) will generate a reset, even if the clock is not
running. Shorter pulses are not guaranteed to generate a reset. When the applied signal
reaches the Reset Threshold Voltage – V
RST on its positive edge, the delay counter starts the
MCU after the time-out period t
TOUT has expired.
Figure 10-4. External Reset During Operation
10.2.3
Brown-out Detection
ATmega8A has an On-chip Brown-out Detection (BOD) circuit for monitoring the V
CC level dur-
ing operation by comparing it to a fixed trigger level. The trigger level for the BOD can be
selected by the fuse BODLEVEL to be 2.7V (BODLEVEL unprogrammed), or 4.0V (BODLEVEL
programmed). The trigger level has a hysteresis to ensure spike free Brown-out Detection. The
hysteresis on the detection level should be interpreted as V
BOT+ = VBOT + VHYST/2 and VBOT- =
V
BOT - VHYST/2.
The BOD circuit can be enabled/disabled by the fuse BODEN. When the BOD is enabled
(BODEN programmed), and V
CC decreases to a value below the trigger level (VBOT- in Figure 10-
5), the Brown-out Reset is immediately activated. When V
CC increases above the trigger level
(V
BOT+ in Figure 10-5), the delay counter starts the MCU after the time-out period tTOUT has
expired.
The BOD circuit will only detect a drop in V
CC if the voltage stays below the trigger level for lon-
ger than t
BOD given in Table 25-3 on page 247.
RESET
TIME-OUT
INTERNAL
RESET
t
TOUT
V
POT
V
RST
VCC
CC




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

Does ALLDATASHEET help your business so far?  [ DONATE ]  

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Bookmark   |   Link Exchange   |   Manufacturer List
All Rights Reserved© Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  , Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp  |   Russian : Alldatasheetru.com
Korean : Alldatasheet.co.kr   |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com  |   Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl