XR88C681CP Datasheet, PDF (39/99 Pages) Exar Corporation – CMOS DUAL CHANNEL UART (DUART)

XR88C681
;


#7
CPU
;


#7
#2#
#2
#
:
#7
#2#
#2
#
:
#7
#2#
#2
#
:
#7
#2#
#2
#
:
#
:
8#082
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9B2
Figure 15. A Diagram of Numerous DUARTs Configured in an Interrupt
Daisy Chain (for Z-Mode Operation)
# $$((    #7  $ #
: ( %"   ?$
  % %%   #2#  $ #2 ( %L  ('  $+( $
% +%4
IEI - Interrupt Enable Input
 (% '( (- (  (%  & ( (+     (%
' +(-$   (   ?$ #+  (% (  (%  
-(' C (- D     %3$ (  E%%" +
 (%  "   $
Note:
Those interrupts which have been masked out by the IMR are
still disabled. However, if this input is at a logic “low”, then all
interrupts (whether masked or unmasked) are disabled.
Hence, IEI can act to globally disable all DUART interrupt
requests.
IEO - Interrupt Enable Output
 (% '( (-  (%  & ( (+     (%
' +(-$   (   ?$  (%  (% +
(% ' '$    #2# (  +     ((&
$('  (%  (% C (- D (+  +   +( -
' $(( %  
   $('H% #2# (  (%   -(' C (- D
   $(' (%  E%( -  (  +  

,
 ( " E%$ &   $('" % M% 
%('$
#+  & +  % ' $(( %  +%"     #2 ( ( 
  -(' CD
Note:
Once the IEO pin has toggled “low”, and the CPU has ac-
knowledged the interrupt request and has completed the inter-
rupt service routine, the IEO pin will remain “low” until the user
invokes the “RESET IUS” command (see Table 3). Therefore,
if the DUART is going to operate in the Z-Mode, the user must
include the “RESET IUS” Command at the very end of the
DUART interrupt service routine.
System Level Application of the IEI and IEO pins
Figure 15 $('%  %(% +  % ' '$ ( 
$(%&' ( +% (  #  (% +(-"   +%  
%   (- % (  ((&  (% (% '%  (%
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$(' E%%  ( " (% #2  ( --
CD  (% ( (  " $(%   C ((&D $('
 
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