peb20532 Infineon Technologies Corporation, peb20532 Datasheet - Page 91

• Manufacturer Part Number: peb20532
• Description: 2 Channel Serial Optimized Communication Controller
• Manufacturer: Infineon Technologies Corporation

– an ’RME’ interrupt generated by the SCC, and
– the receive abort indication ’RAB’ in the Receive Status Byte (RSTA).
Additionally an optional ’FLEX’ interrupt is generated prior to ’RME’, indicating that the
maximum receive frame length was exceeded.
Receive operation continues with the beginning of the next receive frame.
4.2
PPP (as described in RFC1662) can work over 3 modes: asynchronous HDLC,
synchronous HDLC, and octet synchronous. The SEROCCO-M supports asynchronous
HDLC PPP over ISDN or DDS circuits as well as bit and octet synchronous HDLC PPP
for use over dial-up connections. The octet synchronous mode of PPP protocol (RFC
1662) supports PPP over SONET applications.
Both the asynchronous HDLC PPP mode, as well as the synchronous HDLC PPP
modes are submodes of the HDLC mode. Either mode is selected by configuring
SEROCCO-M for the standard HDLC mode. In addition the appropriate PPP mode is
selected via bit field ’PPPM’ in register CCR2L.
The SEROCCO-M provides logic to convert an HDLC frame to an ASYNC character
stream with the specified mapping functions. Layer 3 PPP functions are normally
implemented in software.
The PPP-support hardware allows software to perform segmentation and reassembly of
PPP payloads, and allows SEROCCO-M to perform the asynchronous HDLC PPP or the
synchronous HDLC PPP protocol conversions as required for the network interface.
4.2.1
The SEROCCO-M transmits a data block, inserts HDLC Header (Opening Flag), and
appends the HDLC Trailer (CRC, Ending Flag). Zero-bit stuffing algorithm is also
performed. No character mapping is performed. The bit-synchronous PPP mode differs
from the HDLC mode (address mode 0) only in the abort sequence:
HDLC requires at least 7 consecutive ’1’ bits as abort sequence, whereas PPP requires
at least 15 ’1’ bits.
For receive operation SEROCCO-M monitors the incoming data stream for the Opening
Flag (7E Hex) to identify the beginning of a HDLC packet. Subsequent bytes are part of
data and are processed as normal HDLC packet including checking of CRC.
4.2.2
The SEROCCO-M transmits a data block, inserts HDLC Header (Opening Flag), and
appends the HDLC Trailer (CRC, Ending Flag). Beside this standard HDLC operation,
zero-bit stuffing is not performed, but character mapping is performed.
Data Sheet
Point-to-Point Protocol (PPP) Modes
Bit Synchronous PPP
Octet Synchronous PPP
91
Detailed Protocol Description
PEB 20532
PEF 20532
2000-09-14