psf2115 ETC-unknow, psf2115 Datasheet - Page 42

• Manufacturer Part Number: psf2115
• Description: Isdn Adapter Circuit Ipac
• Manufacturer: ETC-unknow

Semiconductor Group
2.2
2.2.1
The D-Channel HDLC controller in the IPAC is responsible for the data link layer using
HDLC/SDLC based protocols.
The IPAC can be configured to support data link layer to a degree that best suits system
requirements. Multiple links may be handled simultaneously due to the address
recognition capabilities, as explained in section 2.2.1.1.
The IPAC supports point-to-point protocols such as LAPB (Link Access Procedure
Balanced) used in X.25 networking.
For ISDN, one particularly important protocol is the Link Access Procedure for the
D channel (LAPD).
LAPD, layer 2 of the ISDN D-channel protocol (CCITT I.441) includes functions for:
– Provision of one or more data link connections on a D channel (multiple LAP).
– HDLC-framing
– Application of a balanced class of procedure in point-multipoint configuration.
The HDLC transceiver in the IPAC performs the framing functions used in HDLC/SDLC
based communication: flag generation/recognition, bit stuffing, CRC check and address
recognition.
The FIFO structure with two 64-byte pools for transmit and receive directions and an
intelligent FIFO controller permit flexible transfer of protocol data units to and from the
2.2.1.1
The HDLC controller can be programmed to operate in various modes, which are
different in the treatment of the HDLC frame in receive direction. Thus, the receive data
flow and the address recognition features can be programmed in a flexible way, to satisfy
different system requirements.
For the address recognition the IPAC contains four programmable registers for individual
SAPI and TEI values SAP1-2 and TEI1-2, plus two fixed values for “group” SAPI and TEI,
SAPG and TEIG.
C system.
Discrimination between the data link connections is performed by means of a data link
connection identifier (DLCI = SAPI + TEI)
D-Channel Operation
Layer-2 Functions for HDLC
Message Transfer Modes
42
Functional Description
PSB 2115
PSF 2115
11.97