XR68C681J-F Datasheet, PDF (35/75 Pages) Exar Corporation – CMOS Dual Channel UART(DUART)

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”
t_CLK - X1/CLK (External) High or Low Time
    &% $& (' -('  -  ' +
(% '('(&  +" _'3" _{''"  $} +_' ((%  $$ (
$   %     $(' ( + '( &  (%
 '%   ((      + (  
  %(-  ($    5.
:7 ( % %($   
(-  $  %%
f_CLK - X1/CLK Crystal High or Low Time
 (%  %'(+(%    - + +C '(%
(%%(    5.
:7 ( " ( (  '&%
%'(  ($ : (  %(-   +"   %
'  & &    $ = 9G   (% ( 
t_CTC - Counter/Timer External Clock High or Low
Time - IP2 Input
 (%  '%   ((      + (
    %(- " ( - ($    #, ( + % &  

 .(" ' %($    (-  $  %%
,%     (% (( %  ( % ( (  
 _5"  (' (%    %' %%'($ (  
#, ( 
f_CTC - Counter/Timer External Clock Frequency - IP2
Input
 (%  '%   ((    ( 
+C '& ( - ($    #, ( " + % &  

 .(   %' %('& %%    %(- 
( +C '&   = 9G '  ($    #,
( "  $ %(  &  $$ &  
 .(
 (% %' (%  $     _5"  (' %
%'(+(% ((%  %(- % ($  #,    ( 
( %" + %    !  ''3 %' +  %(
 $ '(%
t_RTX - RXC and TXC (External) High or Low Time -
via IP2, IP3, IP4 and IP5
 (% %' '%   ((      + (   
%(- " ( - ($    -  % (  ( %"
#,  #,6" + % %    %(  $ '( ''3
%'" ' %($    (-   %  (% %' %
 ( % (  
_
"   - ( (% % (% 
(  ( #,
 
16