XR68C681 View Datasheet(PDF) - Exar Corporation

Part Name

Description

MFG CO.

XR68C681

CMOS Dual Channel UART(DUART)

Exar Corporation 

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XR68C681

D.8 Explanation of Clock Timing Signals

  % +  (% %'( (%  !(      %'(+('(    ((-
 *'3 % #  

%"  (% %L' %    %' + '%($ '+%( & % %%

Symbol


:7

+
:7




+


5

+5

+5  /5

+5  5

Parameter

5.
:7 2! 9(-  : (

5.
:7
&%  2! C'&

.( 2!
'3 9(-  : ( 

#, #

.( 2!
'3 C'&  #,

#

5
$ 5
2! 9(-  : (  (

#," #,1" #,= $ #,6

5
$ 5
2! C'&  ( #,"

#,1" #,=" $ #,6

/5

5

Min.















Limits

Typ.

1/</=

Max.

=

=





Units

%

9G

%

9G

%

9G

9G

Table 11. The XR68C681 Data Sheet presents the following parameter specifications, in the

“AC ELECTRICAL CHARACTERISTICS”

tCLK - X1/CLK (External) High or Low Time

   &% $&(' -('  -  ' +

(% '('(&  +" '3" ''" $ +' ((%  $$ (

$  %     $(' ( +'( &  (%

 '%   ((     + (  

  %(- ($    5.
:7 ( % %($   

(- $  %%

fCLK - X1/CLK Crystal High or Low Time

 (%  %'(+(%   - + +C'(%

(%%(    5.
:7 (" ( (  '&%

%'(  ($ : ( %(-  +"   %

' & &   $ = 9G   (% (

tCTC - Counter/Timer External Clock High or Low

Time - IP2 Input

 (%  '%   ((     + (

    %(-" (- ($    #, ( + % &  

.(" ' %($    (- $  %%

,%     (% (( %  (% ( (  

 5"  (' (%   %' %%'($ (  

#, (

fCTC - Counter/Timer External Clock Frequency - IP2

Input

 (%  '%   ((    (

+C'& (- ($    #, (" + % &  

.(   %' %('& %%    %(-

( +C'&   = 9G '  ($    #,

(" $ %(  & $$ &  
.(

 (% %' (%  $     5"  (' %

%'(+(% ((%  %(-% ($  #,    (

(%" + %    ! ''3 %' + %(

$ '(%

tRTX - RXC and TXC (External) High or Low Time -

via IP2, IP3, IP4 and IP5

 (% %' '%   ((     + (   

%(-" (- ($    - % ( (%"

#,  #,6" + % %   %( $ '( ''3

%'" ' %($    (-   %  (% %' %

 (% (  

"   - ( (% % (% 

( ( #,

 

16

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