Motor de Búsqueda de Datasheet de Componentes Electrónicos
Selected language     Spanish  ▼

Delete All
ON OFF
ALLDATASHEET.ES

X  

Preview PDF Download HTML

MC68HC908GR16A Datasheet(PDF) 60 Page - Freescale Semiconductor, Inc

No. de Pieza. MC68HC908GR16A
Descripción  M68HC08 Microcontrollers
Descarga  270 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Fabricante  FREESCALE [Freescale Semiconductor, Inc]
Página de inicio  http://www.freescale.com
Logo 

MC68HC908GR16A Datasheet(HTML) 60 Page - Freescale Semiconductor, Inc

Zoom Inzoom in Zoom Outzoom out
 60 / 270 page
background image
Clock Generator Module (CGM)
MC68HC908GR16A Data Sheet, Rev. 1.0
60
Freescale Semiconductor
4.3.4 Acquisition and Tracking Modes
The PLL filter is manually or automatically configurable into one of two operating modes:
Acquisition mode — In acquisition mode, the filter can make large frequency corrections to the
VCO. This mode is used at PLL start up or when the PLL has suffered a severe noise hit and the
VCO frequency is far off the desired frequency. When in acquisition mode, the ACQ bit is clear in
the PLL bandwidth control register. (See 4.5.2 PLL Bandwidth Control Register.)
Tracking mode — In tracking mode, the filter makes only small corrections to the frequency of the
VCO. PLL jitter is much lower in tracking mode, but the response to noise is also slower. The PLL
enters tracking mode when the VCO frequency is nearly correct, such as when the PLL is selected
as the base clock source. (See 4.3.8 Base Clock Selector Circuit.) The PLL is automatically in
tracking mode when not in acquisition mode or when the ACQ bit is set.
4.3.5 Manual and Automatic PLL Bandwidth Modes
The PLL can change the bandwidth or operational mode of the loop filter manually or automatically.
Automatic mode is recommended for most users.
In automatic bandwidth control mode (AUTO = 1), the lock detector automatically switches between
acquisition and tracking modes. Automatic bandwidth control mode also is used to determine when the
VCO clock, CGMVCLK, is safe to use as the source for the base clock, CGMOUT. (See 4.5.2 PLL
Bandwidth Control Register.) If PLL interrupts are enabled, the software can wait for a PLL interrupt
request and then check the LOCK bit. If interrupts are disabled, software can poll the LOCK bit
continuously (for example, during PLL start up) or at periodic intervals. In either case, when the LOCK bit
is set, the VCO clock is safe to use as the source for the base clock. (See 4.3.8 Base Clock Selector
Circuit.) If the VCO is selected as the source for the base clock and the LOCK bit is clear, the PLL has
suffered a severe noise hit and the software must take appropriate action, depending on the application.
(See 4.6 Interrupts for information and precautions on using interrupts.)
The following conditions apply when the PLL is in automatic bandwidth control mode:
•The ACQ bit (See 4.5.2 PLL Bandwidth Control Register.) is a read-only indicator of the mode of
the filter. (See 4.3.4 Acquisition and Tracking Modes.)
•The ACQ bit is set when the VCO frequency is within a certain tolerance and is cleared when the
VCO frequency is out of a certain tolerance. (See 4.8 Acquisition/Lock Time Specifications for
more information.)
The LOCK bit is a read-only indicator of the locked state of the PLL.
The LOCK bit is set when the VCO frequency is within a certain tolerance and is cleared when the
VCO frequency is out of a certain tolerance. (See 4.8 Acquisition/Lock Time Specifications for
more information.)
CPU interrupts can occur if enabled (PLLIE = 1) when the PLL’s lock condition changes, toggling
the LOCK bit. (See 4.5.1 PLL Control Register.)
The PLL also may operate in manual mode (AUTO = 0). Manual mode is used by systems that do not
require an indicator of the lock condition for proper operation. Such systems typically operate well below
fBUSMAX.


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



Número de Pieza relacionado

Part NumberComponents DescriptionHtml ViewManufacturer
MC68HC08AS32AMicrocontrollers 1 2 3 4 5 MoreMotorola, Inc

Enlace URL




Privacy Policy
ALLDATASHEET.ES
Does ALLDATASHEET help your business so far?  [ DONATE ]  

Todo acerca de Alldatasheet   |   Publicidad   |   Contáctenos   |   Política de Privacidad   |   Favorito   |   Intercambio de Enlaces   |   Lista de Fabricantes
All Rights Reserved© Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : 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  |   Vietnamese : Alldatasheet.vn