C165UTAH Datasheet, PDF (374/539 Pages) Infineon Technologies AG – EMBEDDED C166 WITH USART IOM-2 AND HDLC SUPPORT

C165UTAH
IOM-2 Interface Controller
The HDLC controller perform the framing functions used in HDLC based communication:
flag generation/recognition, bit stuffing, CRC check and address recognition.
One 8 byte FIFO for the receive and one for the transmit direction is available for each
HDLC controller.
Note: In the following the description is focused on one HDLC controller only. The same
information applies to all other HDLC controller as well, since they are identical
with the exception of TIC Bus D-Channel Access Control (as noted above).
16.7.1 Message Transfer Modes
A 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.
The structure of a LAPD two-byte address is shown below.
High Address Byte
SAPI1, 2, SAPG
C/R 0
Low Address Byte
TEI 1, 2, TEIG
EA
For the address recognition the HDLC controller contains four programmable registers
for individual SAPI and TEI values (SAP1, 2 and TEI1, 2), plus two fixed values for the
“group” SAPI (SAPG = ’FE’ or ’FC’) and TEI (TEIG = ’FF’).
The received C/R bit is excluded from the address comparison. EA is the address field
extension bit which is set to ’1’ for LAPD protocol.
There are 5 different operating modes which can be selected via the mode selection bits
MDS2-0 in the MODEH register:
16.7.1.1 Non-Auto Mode (MDS2-0 = ’01x’)
Characteristics: Full address recognition with one-byte (MDS = ’010’) or
two-byte (MDS = ’011’) address comparison
All frames with valid addresses are accepted and the bytes following the address are
transferred to the µP via RFIFO.
16.7.1.2 Transparent Mode 0 (MDS2-0 = ’110’).
Characteristics: no address recognition
Every received frame is stored in RFIFO (first byte after opening flag to CRC field).
16.7.1.3 Transparent Mode 1 (MDS2-0 = ’111’).
Characteristics: SAPI recognition
Data Sheet
374
2001-02-23