Cirrus Logic EP93xx - Manual (Page 327)

DS785UM1 9-25
Copyright 2007 Cirrus Logic
1/10/100 Mbps Ethernet LAN Controller
EP93xx User’s Guide
9
9
9
9.2.3.6 Receive Frame Pre-Processing
The MAC pre-processes all incoming receive frames. First the frame is either passed on to
the next level or discarded according to the destination address filter. The next decision is
whether to accept the frame. A frame is accepted when the frame data are brought into MAC
through internal memory. The final step in frame pre-processing is the decision on causing an
interrupt. These pre-processing steps are detailed in
Figure 9-12 .
Figure 9-12. Receive Frame Pre-processing
In c o m i n g F r a m e
D e s t i n a t i o n
A d d r e s s
F i l t e r
P r o m i s c u o u s A
IA H a s h A
M u l t i c a s t A
In d i v i d u a l A
B r o a d c a s t A
F i l t e r T a p s :
If t h e f i l t e r i s n o t p a s s e d ,
t h e f r a m e i s d i s c a r d e d .
F i l t e r P a s s e d
A c c e p t ( A )
M a s k
C R C R u n t A
R u n t A
A c c e p t M a s k s :
A c c e p t M a s k
N O T
P A S S E D
A c c e p t M a s k
P A S S E D
S t a t u s i n R x E v e n t
a n d t h e F r a m e B o d y
i s A c c e p t e d i n t o t h e c h i p
i E
M a s k
i E - M a s k T a p s :
In t e r r u p t i f M a s k O K
f r a m e
d i s c a r d e d
F r a m e i s p a s s e d
t o h o s t m e m o r y
b y d e s c r i p t o r
p r o c e s s o r
R e c e i v e S t Q i E
E n d O f S r e a m i E