Intel 81342 Developer's Manual page 892

1 5 . 4 . 4 U A R T x I n t e r r u p t I d e n t i f i c a t i o n R e g i s t e r
T h e I I R r e g i s t e r i s r e a d t o d e t e r m i n e t h e t y p e a n d s o u r c e o f U A R T i n t e r r u p t s . T o b e
1 6 5 5 0 c o m p a t i b l e , t h e l o w e r 4 b i t s ( 0 - 3 ) o f t h e I I R r e g i s t e r a r e p r i o r i t y e n c o d e d a s
s h o w n i n
o r m o r e i n t e r r u p t s r e p r e s e n t e d b y b i t s ( 0 - 3 ) o c c u r , o n l y t h e i n t e r r u p t w i t h t h e h i g h e s t
p r i o r i t y i s d i s p l a y e d . T h e u p p e r 4 b i t s , ( 4 - 7 ) a r e n o t p r i o r i t y e n c o d e d . T h e s e b i t s
a s s e r t s / d e a s s e r t s i n d e p e n d e n t l y o f t h e l o w e r 4 b i t s .
B i t 0 ( n I P ) i s u s e d t o i n d i c a t e t h e e x i s t e n c e o f a n i n t e r r u p t i n t h e p r i o r i t y e n c o d e d b i t s
( 0 - 3 ) o f t h e I I R r e g i s t e r . A l o w s i g n a l o n t h i s b i t i n d i c a t e s a n e n c o d e d i n t e r r u p t i s
p e n d i n g . W h e n t h i s b i t i s h i g h , n o e n c o d e d i n t e r r u p t i s p e n d i n g , r e g a r d l e s s o f t h e s t a t e
o f t h e o t h e r 3 b i t s . I P # h a s n o e f f e c t o r a s s o c i a t i o n w i t h t h e u p p e r b i t s f o u r b i t s ( 4 - 7 )
w h i c h a s s e r t / d e a s s e r t i n d e p e n d e n t l y o f I P # .
I n o r d e r t o m i n i m i z e s o f t w a r e o v e r h e a d d u r i n g d a t a c h a r a c t e r t r a n s f e r s , t h e U A R T
p r i o r i t i z e s i n t e r r u p t s i n t o f o u r l e v e l s ( l i s t e d i n
R e g i s t e r D e c o d e " o n p a g e 8 9 3
r e g i s t e r . T h e I n t e r r u p t I d e n t i f i c a t i o n r e g i s t e r ( I I R ) s t o r e s i n f o r m a t i o n i n d i c a t i n g t h a t a
p r i o r i t i z e d i n t e r r u p t i s p e n d i n g a n d t h e s o u r c e o f t h a t i n t e r r u p t .
T a b l e 5 6 7 . U A R T x I n t e r r u p t I d e n t i f i c a t i o n R e g i s t e r - ( U x I I R )
e s
3 1
u t
P
i b
r v
I O
t r
A t
e s
u t
I
P C i b
n a
t r
A t
U n i t #
0
1
B i t
31:8
7:6
5
4
3
2:1
0
®
I n t e l 8 1 3 4 1 a n d 8 1 3 4 2 I / O P r o c e s s o r s
D e v e l o p e r ' s M a n u a l
8 9 2
T a b l e 5 6 8 , " I n t e r r u p t I d e n t i f i c a t i o n R e g i s t e r D e c o d e " o n p a g e 8 9 3
) a n d r e c o r d s t h e s e i n t h e I n t e r r u p t I d e n t i f i c a t i o n
2 8 2 4
r v r v r v r v r v r v r v r v r v r v r v
n a n a n a n a n a n a n a n a n a n a n a
®
I n t e l X S c a l e C o r e i n t e r n a l b u s a d d r e s s
+ 2 3 0 8 H ( D L A B = x )
+ 2 3 4 8 H ( D L A B = x )
D e f a u l t
00 0000h Reserved
FIFO Mode Enable Status (FIFOES[1:0]):
00 = Non-FIFO mode is selected
00
01 = Reserved
2
10 = Reserved
11 = FIFO mode is selected (TRFIFOE = 1)
0 Reserved
2
Autobaud Lock (ABL)
0
0 = Autobaud circuitry has not programmed Divisor Latch registers (DLL/DLH)
2
1 = Divisor Latch registers (DLL/DLH) programmed by autobaud circuitry
Time Out Detected (TOD):
0
0 = No time out interrupt is pending
2
1 = Time out interrupt is pending. (FIFO mode only)
Interrupt Source Encoded (IID[1:0]): indicates a Modem Status Interrupt when the
IP# bit is low. When IP# bit is high, there is no Interrupt.
00 = Modem Status (CTS, DSR, RI, DCD modem signals changed state)
0
2
01 = Transmit FIFO requests data
10 = Received Data Available
11 = Receive error (Overrun, parity, framing, break, FIFO error)
Interrupt Pending (IP#):
1
0 = Interrupt is pending. (Active low)
2
1 = No interrupt is pending
T a b l e 5 6 8 , " I n t e r r u p t I d e n t i f i c a t i o n
2 0 1 6 1 2
r v r v r v r v r v r v r v r v r v r v
n a n a n a n a n a n a n a n a n a n a
A t t r i b u t e L e g e n d :
R V = R e s e r v e d
P R = P r e s e r v e d
R S = R e a d / S e t
D e s c r i p t i o n
®
I n t e l 8 1 3 4 1 a n d 8 1 3 4 2 — U A R T s
. W h e n t w o
8 4 0
r v r v r o r o r v r o r o r o r o r o
n a n a n a n a n a n a n a n a n a n a
R W = R e a d / W r i t e
R C = R e a d C l e a r
R O = R e a d O n l y
N A = N o t A c c e s s i b l e
D e c e m b e r 2 0 0 7
O r d e r N u m b e r : 3 1 5 0 3 7 - 0 0 2 U S