peb20525 Infineon Technologies Corporation, peb20525 Datasheet - Page 96

• Manufacturer Part Number: peb20525
• Description: 2 Channel Serial Optimized Communication Controller For Hdlc/ppp
• Manufacturer: Infineon Technologies Corporation

4.4.1
Initially (i.e. after RESET), the LAP controllers of the two serial channels are configured
to function as a combined (primary/secondary) station, where they autonomously
perform a subset of the balanced X.25 LAPB/ISDN LAPD protocol.
Reception of Frames:
The logical processing of received S-frames is performed by the SCC without
interrupting the host. The host is merely informed by interrupt of status changes in the
remote station (receiver ready / receiver not ready) and protocol errors (unacceptable
N(R), or S-frame with I-field).
I-frames are also processed autonomously and checked for protocol errors. The I-frame
will not be accepted in the case of sequence errors (no interrupt is forwarded to the host),
but is immediately confirmed by an S-response. If the host sets the SCC into a ‘receive
not ready’ status, an I-frame will not be accepted (no interrupt) and an RNR response is
transmitted. U-frames are always stored in the RFIFO and forwarded directly to the host.
The logical sequence and the reception of a frame in auto mode is illustrated in
Figure
Note: The state variables N(S), N(R) are evaluated within the window size 1, i.e. the
Data Sheet
SCC checks only the least significant bit of the receive and transmit counter
regardless of the selected modulo count.
47.
Full-Duplex LAPB/LAPD Operation
96
Detailed Protocol Description
PEB 20525
PEF 20525
2000-09-14