pef20320 Infineon Technologies Corporation, pef20320 Datasheet - Page 81

• Manufacturer Part Number: pef20320
• Description: Multichannel Network Interface Controller For Hdlc With 32 Channels
• Manufacturer: Infineon Technologies Corporation

HDLC
Receive Direction
General Features
In receive direction:
1. The starting and ending flag (7E
2. A change of the interframe time-fill is recognized and reported by an interrupt.
3. The zero insertions (a ‘0’-bit after five ‘1’s within a frame) are extracted.
4. The FCS at the end of a frame is checked, it is (optionally) transferred to the shared
5. The number of the bits within a frame (without zero insertions) is checked to be
6. The number of bytes within a frame is checked to be smaller than MFL + 1 (after
7. The number of bits within a frame after extraction of ‘0’ insertions is checked
(case NSF = 0 only)
(only for CS = 0)
(case NSF = 1 & CS = 1 only) check a’) 8 for CRC = x (ignored)
8. The occurrence of an abort flag (7F
More detailed description of the individual features:
1. a. A frame is supposed to have started if after a sequence of 0111 1110 in the receive
User’s Manual
and extracted.
memory together with the data.
divisible by 8.
extraction of ‘0’ insertions).
to be greater than (case NSF = 0 only)
b. A frame is supposed to have stopped if a sequence of 0111 1110 or 0111 1111 is
c. The ending flag of a frame may be the starting flag of the next frame (shared flags
data stream neither FC
have started with the first bit after the closing ‘0’ of the sequence.
found in the data stream after the frame has started. The last bit of the frame is
supposed to be the bit preceding the ‘0’ in the above sequences. The cases of
sequences 0111 1110 1111 111 and 0111 1110 0111 1111 are also supposed to
be frames of bit length – 1 and 0 respectively.
A frame is also supposed to have stopped if more than MFL bytes were received
since the start of the frame and it wasn’t stopped yet.
supported).
H
nor FD
check a) 16 for CRC = 0
check b) 32 for CRC = 0
H
before and after a frame) is recognized
H
H
nor 7E
) ending a frame is checked.
32 for CRC = 1
48 for CRC = 1
81
H
has occurred. The frame is supposed to
Functional Description
PEB 20320
01.2000