PEB2085 SIEMENS [Siemens Semiconductor Group], PEB2085 Datasheet - Page 187

• Manufacturer Part Number: PEB2085
• Description: ISDN SubscribernAccess Controller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

3.4.1
Assuming a normally running communication link (layer-1 activated, layer-2 link established,
TEI assigned), figure 79 illustrates the transfer of an I-frame via the D channel. The transmitter
is shown on the left and the receiver on the right, with the interaction between the
microcontroller system and the ISAC-S in terms of interrupt and command stimuli.
When the frame (excluding the CRC field) is not longer than 32 bytes, the whole frame is
transferred in one block. The reception of the frame is reported via the Receive Message End
(RME) interrupt. The number of bytes stored in RFIFO can be read out from RBCL. The
Receive Status Register (RSTA) includes information about the frame, such as frame aborted
yes/no or CRC valid yes/no and, if complete or partial address recognition is selected, the
identification of the frame address.
Depending on the HDLC message transfer mode, the address and control field of the frame
can be read from auxiliary registers (SAPR and RHCR), as shown in figure 80.
Figure 79
Transmission of an I-Frame in the D Channel (Subscriber to Exchange)
Semiconductor Group
System
HDLC Frame Reception
µ
C-
:= Data Transfer *) In Auto Mode the "RR" Response will be Transmitted Autonomously
ISAC -S
(TE)
R
LAPD Link
187
ISAC
(LT-S)
R
-S
Operational Description
System
µ
ITD02391
C-